Performance Nutrition
Applying the Science of Nutrient Timing
by Krista G. Austin and Bob Seebohar
200 Pages
Optimize training, enhance recovery, and improve performance with Performance Nutrition: Applying the Science of Nutrient Timing. Based on the most current research in nutrient timing, Performance Nutrition blends theory with applied content and real-life examples to help nutritionists, athletes, and coaches design nutrition plans based on each athlete’s individual needs and the specific demands of the sport.
While other texts may provide a brief discussion of nutrient timing as a tool for improving sport performance, Performance Nutrition: Applying the Science of Nutrient Timing focuses solely on this newly developing facet of sport nutrition. Distinguished authors Krista Austin (a physiologist and nutritionist) and Bob Seebohar (a sport dietitian and USA Triathlon elite coach) share their extensive practical experience with athletes at all levels from recreational through professional. They provide specific nutrient timing recommendations for a wide range of sport types, including endurance, strength and power, combative (weight classified), and team sports.
In particular, you will learn information on using nutrient timing theory to counteract altitude, heat and humidity, cold exposure, and air pollution. A chapter devoted to competition-day guidelines will help you keep your athletes hydrated, energized, and ready to perform. Plus, nutritional timelines, highlighted in special callout boxes and placed at the edge of the page for quick reference, offer visual plans of what athletes should eat in the hours leading up to and during competition. Practical and user friendly, this text also includes “In Practice” application exercises, mini-case studies, and four extended case studies to assist in translating the information to your own practice.
Incorporating nutrient ingestion timing into your athlete’s training program can promote enhanced recovery, create positive training adaptations, improve body composition, support immunity, and ultimately enhance performance. With Performance Nutrition: Applying the Science of Nutrient Timing, you will gain the foundational knowledge and practical techniques to develop individualized nutrition programs to improve training, performance, and recovery.
Chapter 1. Principles of Nutrient Timing
Physiological Basis for Nutrient Timing
Nutrient Timing, Training, and Performance
Nutrient Timing, Food Intake, and Body Composition
Conclusion
Chapter 2. Assessing Sport Performance
Sport Performance Analysis
Creating a Toolbox for Performance Nutrition Assessment
Conclusion
Chapter 3. Psychology and Sport Nutrition
Age and Nutrition
Hunger and Eating Habits
Preparing for Nutrition Change
Conclusion
Chapter 4. Functionality of Foods
Digestion of the Macronutrients
Understanding Carbohydrate
Understanding Protein
Understanding Fat
Fuel Oxidation
Fat and Carbohydrate Oxidation During Exercise
Using the Functional Foods
Conclusion
Chapter 5. Timing Fluid Intake
Testing Hydration Status
Hydration and Performance
Hydration Issues
Conclusion
Chapter 6. Macronutrient Timing Strategies
Nutrient Strategies
Pretraining Nutrient Strategies
Nutrient Strategies During Training
Posttraining Nutrient Strategies
Crossover Concept
Conclusion
Chapter 7. Nutrition Periodization
Rationale for Periodization
Athlete Differences
Periodization and Nutrition Planning
In-Season
Off-Season
Conclusion
Chapter 8. Nutritional Supplementation
Evaluating Supplements
Dietary Supplements
Sport Supplements
Ergogenic Aids
Conclusion
Chapter 9. Nutrient Timing in Changing Environments
Altitude
Heat and Humidity
Cold Exposure
Air Pollution
Conclusion
Chapter 10. Competition Day
Combative Sports (Weight Classified)
Strength and Power Sports
Endurance Sports
Team Sports
Long Duration Sports Requiring Concentration
Krista Austin, PhD, CSCS, is an exercise physiologist, nutritionist, and NSCA-certified strength and conditioning specialist. She is also a research associate with the International Center for East African Running Studies.
Austin was a performance nutritionist with the English Institute of Sport, where she provided services to 18 Olympic sports and the England cricket team. Most recently she served as a physiologist with the United States Olympic Committee, where she worked with multiple sports in preparation for the 2008 Olympic Games. In particular, she is well known for her nutrition work with USA Taekwondo.
Austin is owner of Performance & Nutrition Coaching, LLC, which provides physiological testing, nutrition, and coaching education to professional and amateur athletes as well as Olympic national teams, including USA Track & Field, USA Canoe/Kayak, USA Wrestling, and USA Triathlon.
A former collegiate tennis player, she obtained a PhD in movement science from Florida State University and holds a master’s degree in exercise physiology from San Diego State University. She is a member of the American College of Sports Medicine and has also served as associate editor of the International Journal of Sport Nutrition and Exercise Metabolism.
Bob Seebohar, MS, RD, CSSD, CSCS, is a board-certified specialist in sport dietetics and owner of Fuel4mance, a leading nutrition consulting firm serving amateur and elite athletes. Seebohar is the former director of sport nutrition for the University of Florida and most recently served as a sport dietitian for the U.S. Olympic Committee. In 2008, Seebohar traveled to the Summer Olympic Games in Beijing as a sport dietitian for the U.S. Olympic team and as the personal sport dietitian for the Olympic triathlon team. Seebohar currently consults as a sport dietitian for US Sailing (Olympic and Paralympic sailors) and the USA Triathlon national athletes and 2012 and 2016 Olympic team athletes.
Seebohar has worked with athletes in a variety of sports, including triathlon, duathlon, ultrarunning and cycling, track and field, marathon, mountain biking, road and track cycling, cross country, swimming, football, taekwondo, motocross, tennis, wrestling, weightlifting, rowing, sailing, canoeing, and kayaking. He has worked with people of all ages and abilities, including high school students, recreationally active adults, professional athletes, and Olympians.
Seebohar holds a bachelor's degree in exercise and sport science and master’s degrees in health and exercise science and food science and human nutrition. He is a registered dietitian, exercise physiologist, certified strength and conditioning specialist, and a high-performance triathlon coach.
Beginning as a competitive soccer player in his youth, Seebohar turned to endurance sports in 1993. In 1996 he represented the United States as a member of the 1996 duathlon team at the 1996 World Championships. He has competed in numerous endurance events, including the Boston Marathon, six Ironman races, the Leadville 100-mile trail race, and the Leadville 100-mile mountain bike race. In 2009, Seebohar became a Leadman, completing all six of the Leadville endurance events in 7 weeks.
He lives in Littleton, Colorado, where he enjoys training for ultraendurance running and cycling events and coaching youth in soccer and triathhlon.
Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
Learn more about Performance Nutrition.
Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
Learn more about Performance Nutrition.
Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
Learn more about Performance Nutrition.
Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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Physiological basis for nutrient timing
Several lines of scientific evidence provide the basis for timing nutrient ingestion.
Several lines of scientific evidence provide the basis for timing nutrient ingestion. The body's response to exercise in terms of hormone control and muscle function and its response to different types of carbohydrate and protein create the foundation for understanding how timing nutrition specifically to the muscles' functional needs is optimal for an athlete. Together, these responses produce the greatest evidence, which is the effect on body composition, glycogen stores, protein balance, and rehydration.
Hormonal Control
Hormonal responses to exercise are dependent on training intensity, training duration, training volume, and the fitness level of the person. The key hormones involved in the regulation of muscle function are epinephrine, norepinephrine, insulin, cortisol, and glucagon. Figure 1.1 shows how these hormone levels change with increasing exercise duration. The hormones epinephrine and norepinephrine are called neurotransmitters and are responsible for stimulating the breakdown of stored fat and glycogen for use as energy during exercise. With the onset of exercise, epinephrine and norepinephrine rapidly increase.
Insulin is the hormone responsible for the integration of fuel metabolism at rest and during exercise. The levels of insulin determine how much of the body's needed energy will be derived from the breakdown of fat, carbohydrate, and protein. When an athlete is in a fasted state, less insulin is produced, and fats and proteins are recruited to provide fuel for the body. With food consumption, insulin levels increase so that consumed carbohydrate, fat, and protein can be utilized for fuel or stored by the body's tissues. During exercise, insulin allows glucose to be readily used by the body's working tissues. The sensitivity of the muscle cells to insulin increases when exercise is stopped.
The actions of cortisol and glucagon are dependent on the amount of glucose in the blood and on energy availability in the body. Glucagon is increased in response to low blood glucose levels; it is responsible for breaking down carbohydrate stored as glycogen in the liver and facilitating the conversion of amino acids to glucose. Cortisol is the hormone that facilitates the synthesis of glucose from the breakdown of protein and fat in times of a reduced energy state. When blood glucose levels drop too low during exercise, glucagon is increased to promote glycogen release from the liver and, if necessary, works with cortisol to promote the synthesis of glucose from free fatty acids and amino acids.
Muscle Regeneration
A number of factors—from enzymes, to blood flow, to receptors on the muscle cell, to hormone action—are elevated to the greatest extent in the first 45 minutes after exercise stops. Over the next several hours, these factors slowly return to resting levels; thus, the 45 minutes after exercise is considered a window of opportunity for the ingestion of foods that will promote muscle recovery through glycogen replenishment and rehydration.
This response is highly facilitated by the enzyme glycogen synthase and a transporter known as GLUT4, both of which are responsive to insulin and are significantly elevated after exercise. Together glycogen synthase and GLUT4 enhance the uptake of carbohydrate and improve glycogen storage. These actions are further facilitated through insulin, which facilitates carbohydrate uptake and increases the rate of muscle blood flow. This not only helps deliver nutrients to the muscles but also aids in the elimination of metabolic waste that was produced during exercise. In the 45 minutes immediately after exercise, the activity of GLUT4 receptors and levels of glycogen synthase are maximally elevated, allowing insulin to facilitate carbohydrate restoration to the muscle cells and improve recovery from training (figure 1.2).
Types of Carbohydrate and Protein
The functionality of foods is covered in greater detail in chapter 4, but it is important to note here that intake of the right type of carbohydrate is significant evidence for timing nutrient ingestion. In addition, the timing of protein and the type available to the muscle are critical for optimizing adaptations from resistance and cardiovascular training.
As mentioned, insulin is an important hormone in the muscle response after exercise. The rate of posttraining muscle glycogen synthesis has been shown to be proportional to the increase in blood insulin levels. Athletes should therefore select the type of carbohydrate they consume based on how quickly glycogen stores must be replenished, which depends on the amount of time between training sessions. When the next training session will begin determines the type of carbohydrate and insulin response that is desired. For most athletes, muscle glycogen can be sufficiently restored through the use of low to moderate glycemic carbohydrates that do not require a significant spike in insulin and will steadily restore glycogen. This approach will also help to minimize gains in body weight. An example of a postexercise snack that would provide this response is whole wheat bread with almond butter and banana. When glycogen restoration must happen quickly, the best types of carbohydrate to stimulate an increase in blood insulin levels are those that evoke a high glycemic response because of their rapid conversion to glucose in the blood. An example of a postexercise snack that would provide this response is white bread with banana and honey. All are made of simple sugars and have minimal fiber content so that digestion and absorption by the body can be done quickly. The more readily glucose can become available to the working muscles, the faster the rate of glycogen resynthesis can occur and recovery can begin. This is frequently the case for athletes who perform multiple prolonged training bouts within a day or, in the case of a weight-classified sport, athletes who must replenish glycogen stores from having cut weight.
Glycogen restoration may be further enhanced through the ingestion of protein with carbohydrate. This is attributed to the optimization of the insulin response and the suppression of cortisol, which speeds the muscle's recovery process. The availability of essential amino acids (such as those found in dairy and meat products) before and after training is also an important factor in maintaining or increasing muscle protein synthesis. Thus, it is important that the protein source used contain all the essential amino acids. Depending on an athlete's food preferences, this can be accomplished by consistently consuming foods in the daily diet that contain all the essential amino acids or by ensuring that the pre- and posttraining snack contains foods that are a good source of essential amino acids.
Body Composition
Most athletes seek to optimize the ratio of muscle and fat mass in the body because of the positive relationship this has with performance. Studies assessing the patterns of food intake by athletes have shown that eating meals at regular intervals is most optimal for maintaining a high level of muscle mass and a lower level of body fat. These same studies show that most athletes eat infrequently and consume a majority of their calories in a large meal at the end of the day. This leads to large rises in blood glucose that in turn encourage the storage of fat mass. Furthermore, this eating pattern delays energy restoration, and so the body utilizes muscle proteins to make and maintain blood glucose levels, leading to a decrease in muscle mass. For the body to optimize its composition, blood glucose needs to stay stable. When an athlete consumes the energy expended in a training session through frequent eating that revolves around training, the muscles are functionally available and ready to absorb the nutrients ingested, thus helping to maintain stable levels of glucose in the body. Timing nutrient ingestion revolves around the supply and demand for energy production by the working body, which enhance body composition. Improvements in body composition result in an improved ratio of muscle mass to fat mass and in turn directly result in an improved work capacity.
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Posttraining nutrient strategies
The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes.
Recovery is one of the most important factors in the process of adapting to training. The intake of fuel within 45 minutes of training can help optimize the recovery of energy stores, which is important for repairing muscle and maintaining a healthy immune system in athletes. In addition, consuming frequent small meals that contain the appropriate distribution of carbohydrate, protein, and fat also optimizes delivery of energy to the body throughout the remainder of the day to improve recovery and other factors such as body composition, which is critical for successful performance.
Carbohydrate Intake After Training and Competition
Carbohydrates are needed immediately after training or competition in order to begin the glycogen restoration process. Because glycogen stores are used during exercise, supplying the body with sources of carbohydrate is of utmost importance so the athlete can recover glycogen stores faster and be ready for the next session. This is even more important after a prolonged training session, especially if a second training bout is scheduled for the day.
After the initial postworkout consumption of a carbohydrate and protein snack, it is beneficial for athletes not seeking weight loss to eat another 1.0 to 1.2 grams of carbohydrate per kilogram of body weight 2 hours after the initial carbohydrate feeding and repeat throughout the next 6 to 8 hours in 2-hour increments. This strategy will refill glycogen stores the fastest, typically within 12 to 16 hours instead of 24 hours. Choosing any combination of carbohydrate during this time is beneficial as long as the foods are less processed and refined. Ideas include carbohydrate-rich snacks and meals balanced with lean protein such as a lean turkey sandwich with tomato, lettuce, cucumbers, pickles, and mustard; a nonfat milk-based fruit smoothie; a bowl of whole-grain cereal with berries and skim milk; or oatmeal made with skim milk and raisins. The goal is to maximize glycogen repletion, so eating smaller snacks or meals is preferred over larger ones that fill you up so much that you cannot eat again in another 2 hours.
Protein Intake After Training and Competition
Protein intake in the timeline immediately after training or competition can be used to repair muscle and restore muscle glycogen. Up to 20 grams of protein has been proven beneficial in facilitating carbohydrate uptake by the muscles, believed to result from protein's effect on the interaction of insulin with carbohydrate. An athlete's body size, training duration and intensity, and need to manage body weight will determine how much protein and carbohydrate is taken in. Athletes must learn to relate the size of a posttraining recovery snack to the intensity of the exercise bout. This is best exemplified by comparing a technique session to a high-intensity training session. After a technique session, a simple snack such as a yogurt that provides 6 to 8 grams of protein is sufficient, whereas a recovery shake containing 20 grams of protein would be appropriate after a high-intensity training session.
This rule can also be applied to athletes who are in a weight-loss phase. Regardless of training intensity, since energy intake must be reduced, the size of the postexercise snack must also be reduced. Thus, after a high-intensity session, 6 to 8 grams of protein would be sufficient, and the snack after a technique session could be completely eliminated. For athletes who must monitor body weight closely, a key component is minimizing food intake in the 2 hours after a resistance training session. This is the critical time period for increasing muscle synthesis. Although it would take multiple days and a significant increase in caloric intake to increase body mass, genetically some athletes are predisposed to building muscle mass rather easily. Thus, these athletes must do everything possible to keep this from happening, particularly in sports where a light body mass is required.
The second opportunity to take in protein is a meal within 2 hours after training. Protein at this point can be used to facilitate weight control or minimize the glycemic response of a meal, or it can serve a more minimal role in making a meal palatable. For athletes seeking to control body weight, protein can be increased in a meal to provide satiety and slow the rate at which glucose enters the blood. This will help optimize body composition, create satiety, and send the appropriate signals to the brain that indicate blood glucose is stable, and thus signals for hunger are not initiated. When weight loss is desired, the combination of protein, fiber, and water can create a sensation of fullness for a prolonged period of time. Protein has also been shown to help sustain lean body mass and cause a greater amount of fat loss. This is thought to be a result of its inefficient breakdown process, and thus very little usable energy is consumed, which helps further create a caloric deficit.
Athletes who need to keep body weight up or significantly replenish carbohydrate stores should minimize the amount of protein consumed in the recovery meal. Although protein can be used to make a meal palatable, these athletes need to minimize the satiety component. For athletes needing to gain weight, they must continue eating to create a positive energy balance. Athletes who deplete carbohydrate stores must consume enough food to fully restore muscle glycogen. Athletes competing in tournaments with bouts of high-intensity exercise for several hours daily need to pay particular attention to glycogen replenishment. This is most frequently seen in team sports and strength and power-type technical sports such as tennis and badminton.
The other role of protein is to minimize the glycemic response of snacks taken in between meals. This is important when trying to optimize body composition. Protein should be included in any snack eaten more than an hour before training, and it should make up at least 25 percent of the caloric value of the snack. This not only helps minimize an overconsumption of carbohydrate and increased snacking but also aids in satiety and slows the rate at which food empties from the stomach, thus controlling the glycemic response.
Fat Intake After Training and Competition
It has been theorized that intramuscular triglycerides (IMTGs) provide an energy source during exercise. These fats, stored inside the muscle, can decrease during exercise; thus, some researchers have studied the replenishment of IMTGs in the posttraining period. Although it has been shown that a high-carbohydrate and low-fat diet in the posttraining period may not fully replenish IMTGs, and moderate carbohydrate increases the stores more effectively, it is still unknown how important replenishing IMTG stores really is in terms of affecting performance.
Minimizing the amount of fat consumed in the first hour after a training session is recommended; the focus should be on ingesting carbohydrate, protein, fluid, and sodium. Fat—particularly omega-3 and monounsaturated—should be consumed at regular meals and snacks to provide a balanced macro-nutrient profile thereafter. Table 6.1 summarizes the nutrients that should be consumed in the period after training.
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Nutrient timing for heat and humidity
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue.
The body naturally produces heat at rest as a result of breaking down energy stores. During exercise the amount of heat produced is proportional to exercise intensity, and this raises a person's core body temperature. As the brain senses an increase in core temperature, blood flow is increased and taken away from the core of the body. This results in an enhanced cardiac output, which is evidenced by an increased heart rate at rest and during exercise. The blood is distributed to working muscles to facilitate their function by maintaining oxygen delivery and increasing the removal of waste and heat. Blood flow will also increase to the body's surface (skin), where heat is then removed through sweating.
The body uses four different methods—evaporation, convection, radiation, and conduction—to remove heat from the body so that severe hyperthermia (very high increases in body temperature) does not occur. Evaporation removes heat through sweating and is highly dependent on the amount of moisture in the air. In hot, dry conditions sweat is quickly dissipated; as the moisture content of air (i.e., humidity) increases, sweat cannot be readily removed, and less heat can be eliminated through this method. In a hot, dry environment evaporation accounts for up to 90 percent of heat loss. When humidity increases to greater than 50 percent, the body must increase reliance on other methods to remove heat. If this is not feasible, heat will continue to be stored by the body, and exercise intensity and duration will eventually be reduced.
The other means of removing heat is through nonevaporative methods that require an increase in heat loss to the environment or an object that is cooler than the body's temperature. In radiation, heat is given off by one object (the athlete) and is absorbed by the environment or another object that the person is in contact with (e.g., the ground). In convection, heat is lost by a person moving through a current (air or fluid). Conduction is the transfer of heat to another object through touch (e.g., the hand touching a cold surface) and in most situations accounts for very little heat loss.
When athletes move from a cool or moderate temperature to a hot environment, proper acclimatization to the heat over a two-week period before competing or training at full volume and intensity is probably the most important thing they can do. Athletes who experience hyperthermia when competing or training in the heat have usually not acclimatized appropriately. Acclimatization can be done by slowly increasing training volume and then intensity and by training at the coolest times of the day. The body's response to acclimatization is depicted in figure 9.3.
During the first five days of heat exposure, the adaptations of a decreased heart rate and perceived exertion to a training bout will occur. This is a result of an increase in plasma volume and the start of an increased retention of electrolytes (primarily sodium) in the sweat and urine. By day 10, core body temperature is decreased as the brain resets and increases sweat rate to compensate during exercise. The full increase in sweat rate is completed by day 14. Complete adaptation is also marked by a significant shift from anaerobic to aerobic metabolism and thus a greater reliance on fat as a fuel source rather than carbohydrate. The increased reliance on fat can be highly attributed to a reduction in strain on the body as a result of increased heat removal through a raised sweat rate, a decreased relative exercise intensity, and a decreased number of muscle fibers needed to perform the same amount of work. Together, these markers are evidence of a complete adaptation to the heat.
Energy and Hydration Needs
Ensuring that an athlete takes in adequate fuel and fluid during exercise in the heat is important to minimize injury and prevent premature fatigue. An athlete moving from a cool or moderate temperature to one that is hot experiences several shifts in metabolism that must be accounted for during training. At rest, RMR is decreased on average by approximately 5 percent. This is attributed to a decreased need to maintain body temperature because the environment helps do this; however, a hot environment can lead to decreased appetite, and as a result athletes need to be careful that they meet their energy needs.
Training in the heat increases de-mands on the body's metabolism in proportion to the increase in environmental heat. With a significant shift toward a more anaerobic metabolism, initial exposure results in increased carbohydrate use and decreased fat utilization; an increased sweat rate also leads to greater fluid losses. This happens because the athlete is working at a higher relative percentage of maximal capacity and because an increase in muscle temperature decreases muscle efficiency. When muscle temperature increases, muscle crossbridges fatigue at a higher rate; thus, the number of muscle fibers recruited over time will need to increase so that work capacity can be sustained. Depending on how well athletes acclimatize to a hot environment, they may or may not improve their reliance on fat as a fuel source. However, with heat acclimation, appropriate fueling and hydration strategies, and body-cooling techniques (e.g., cooling vest, cold showers or baths, hand and feet immersion in cool water, cool towels or ice packs), an athlete should be able to train and perform in such a harsh environment.
Because an athlete's body temperature is higher in warmer environments, the desire to eat can be significantly reduced; thus, it is important for an athlete to identify foods and fluids that taste pleasant at rest and during exercise. It is best to have a wide variety of palatable foods and fluids available and to make part of the recovery meal fluid based. Energy needs can be met through several different means. The types of fluid ingested and the amount of residue a food contains should be considered. The first strategy is to increase the calorie content of fluids used to rehydrate (e.g., meal replacements, carbohydrate-electrolyte beverages, juices, smoothies, iced tea). A second option is to increase low-residue foods eaten as snacks every 30 minutes to an hour in between meals. These foods are easier to digest and do not indicate to the receptors of the stomach that it is full. In addition, less heat is produced as these foods digest, and as a result, this will help control body temperature. Examples of high- and low-residue foods are listed in table 4.1 on page 73-74.
It is not uncommon for fluid loss to exceed the amount able to be taken in during training. Fluid ingestion can considerably improve the body's ability to minimize heat storage by helping to maintain sweat rate and providing a cooling sensation when ingesting fluids that are below body temperature. A timeline for fluid ingestion is important for coping with the heat. The timeline needs to ensure that an athlete enters each training session well hydrated and that hydration begins immediately after training and if possible is also incorporated into training. The temperature of a beverage can significantly influence how palatable it will be to an athlete and how quickly it can absorbed by the body. Cool fluids are best when training in a hot environment; when at rest, fluids that are at room temperature or slightly cooled will be better tolerated. The timeline shows guidelines for maintaining hydration when training in a hot environment.
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Competition day nutrition for endurance sports
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing.
Endurance sports cover a variety of events consisting of short-duration (under 2 hours) to multiday competitions and include sports such as running, triathlon, cycling, rowing, canoeing and kayaking, swimming, biathlon, and cross-country skiing. Each endurance sport has its own individual nutrient timing challenges based on the intensity and duration of the competition. A short- and long-course triathlon provides a good overall example of how to implement a nutrient timing system within an endurance sport. Although the sport is triathlon, the system can be applied to many other endurance-classified sports because they share commonalities in energy needs. The main differences will be the length and the logistics of the competition.
Sport: Triathlon, Short and Long Distances
Competition details: There are four main distances in the sport of triathlon. Sprint-distance triathlon races typically involve a quarter- to half-mile swim, 12- to 18-mile bike ride, and 3.1-mile run. The Olympic-distance triathlon includes a 1.5-kilometer swim followed by a 40-kilometer bike ride (in a drafting or nondrafting format) followed by a 10-kilometer run. Half Ironman triathlons involve a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run. Ironman triathlons involve a 2.4-mile swim, 112-mile bike ride, and 26.2-mile run (1 mile = 1.6 kilometers). Competition times greatly depend on the level of athlete, with professionals and elite age-groupers recording faster times and recreational and beginning athletes registering slower times. Sprint-distance events last approximately 55 minutes to 1 hour and 30 minutes, Olympic distances from 1 hour and 45 minutes to 3 hours, half Ironman distances from just under 4 hours to 7 hours, and Ironman distances from just under 8 hours to 17 hours. For recreational triathletes, racing usually begins early in the morning, between 6:00 and 8:00 a.m. Professional triathletes competing in Olympic draft-legal races often start racing later, between 11:00 a.m. and 3:00 p.m. Each event poses different nutrition challenges in terms of nutrient timing.
Energy systems used: The aerobic energy system predominates, but it is important to note that all energy systems are relied on during some events, especially during the start.
Nutrition goals leading up to competition: The main goals for most triathletes include reducing GI distress, maintaining adequate hydration and electrolyte levels, and not gaining weight due to a decrease in energy expenditure during their taper.
The taper itself presents a significant challenge for triathletes. Because the range of the taper is large—4 to 28 days depending on the coach and distance—athletes do not often know how to navigate the time leading up to competition, and thus water retention and feelings of bloating and heaviness are common. Eating will depend somewhat on the length of the taper, but triathletes can use the following nutrition goals:
- Increasing daily salt intake is usually a common practice during the taper, but athletes should try this during quality training sessions well before the race because it sometimes leads to slight bloating and water weight gain.
- A two- or three-day fiber taper can be extremely beneficial for some triathletes who are more susceptible to GI distress or have a sensitive gut. It is recommended to decrease fiber intake by 25 percent each day two or three days out from the race by focusing on more white starch products and juices.
- Maintaining hydration status is important, and overdrinking water is a common practice. If water is used as the primary fluid throughout the day, salty foods should be eaten at the same time in an effort to prevent hyponatremia. It is also recommended that triathletes drink when thirsty and not try to hyperhydrate with water leading up to the race.
- Maintaining energy levels is crucial during the taper so that the craving response is reduced. In an effort to stabilize blood glucose levels, triathletes should combine a source of lean protein, healthy fat, a fruit or vegetable, and a starch during all feedings. Triathletes should avoid eating only a starch by itself because it will raise blood glucose levels quickly and could lead to overeating during the taper.
- Stabilizing body weight is a primary goal of all triathletes leading up to a race, and as mentioned previously, this is typically difficult to control because of decreases in training volume. Athletes should not overeat and try to overcompensate their caloric intake in an effort to load before competition. Most athletes who follow a balanced eating program consisting of moderate carbohydrate, moderate protein, and low to moderate fat should continue this type of eating during their taper. Frequency of eating may be a variable that triathletes can consider changing, meaning they may not need to eat as many times throughout the day. Eating to train during a taper becomes a good mantra to follow, and since training is reduced, so should food intake.
Competition Day
Race-day nutrition is highly individual for all triathletes, and the race distance and start time will dictate much of what a triathlete can consume the morning of a race. The following general recommendations pertain to early-morning races:
- A smaller breakfast made up of moderate carbohydrate, moderate to low protein, and low fat is recommended. A liquid snack or meal such as a smoothie may be beneficial for those who have very sensitive stomachs.
- Athletes should hydrate but should pay attention to not overhydrating with water alone as this can increase the risk of hyponatremia. Consuming water with salty foods or a sports drink with sodium is recommended.
- For athletes competing later in the day, a normal breakfast that has worked for the athlete during higher-intensity training can be eaten followed by an easily digestible snack 1 to 2 hours before the race. Liquid sources are typically preferred.
- After the race, it is common for athletes to forget about their nutrition. The postrace nutrition plan is crucial for allowing an athlete to replenish glycogen and fluid stores. The basic guidelines on what to eat in the first 15 to 60 minutes after a race include higher carbohydrate, moderate protein, and minimal fat and fiber. Athletes should plan ahead of time to ensure that foods or beverages are available after their race. After the initial feeding, athletes should try to eat well-balanced meals consisting of carbohydrate, protein, and fat (specifically omega-3 or monounsaturated) 2 hours after the first postrace feeding.
- If a fiber taper was implemented before a race, it is important to reintroduce fiber slowly into the normal daily nutrition plan by reversing the recommendations stated previously. That is, increase fiber gradually by 25 percent each day after the race to allow the body to get used to the normal amounts without causing GI distress.
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