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Running Mechanics and Gait Analysis With Online Video is the premier resource dedicated to running mechanics and injury prevention. Running continues to be one of the most popular sports, despite the fact that up to 70 percent of runners will sustain overuse injuries during any one-year period. Therefore, it is imperative for health care professionals, coaches, and runners themselves to be informed on injury prevention and optimal treatment. Referencing over 250 peer-reviewed scientific manuscripts, this text is a comprehensive review of the most recent research and clinical concepts related to gait and injury analysis.
Running Mechanics and Gait Analysis With Online Video supplies professionals with an expansive array of clinical applications. Physical therapists and athletic trainers will come away with an understanding of ways to build on standard practice, while runners, coaches, and personal trainers will gain a new appreciation for the performance benefits that gait analysis can provide. The text has the following features:
• A discussion of the complexities of running biomechanics as they relate to muscular strength, flexibility, and anatomical alignment for the purpose of providing an advanced clinical assessment of gait
• Guidelines for assessing, treating, and preventing a range of common and not-so-common running injuries
• A detailed analysis of running biomechanics to help professionals identify the interactions of the kinetic chain and the causes of overuse injuries
• A video library featuring 33 clips that demonstrate the biomechanical patterns discussed in the text
• Documented clinical examples to help practitioners apply the wealth of information in the book to their own practice
Early chapters introduce readers to the basics of running-related injuries, foot mechanics, and shoe selection before progressing to discussions of knee and hip mechanics, ways to influence gait mechanics, and technical aspects of video gait analysis. Via a detailed joint-by-joint analysis, the book pinpoints common problem areas for runners and describes protocols for treatment. Later chapters present case studies of injured runners to guide professionals through a detailed biomechanical analysis and treatment recommendations, and an overview chapter summarizes the interrelationships of movement patterns at each joint with anatomical, strength, flexibility, and kinetic chain factors.
Running Mechanics and Gait Analysis With Online Video is the most comprehensive resource for running-related research. Readers will come away armed with the knowledge and tools to perform an advanced clinical assessment of gait and rehabilitate and prevent running injuries.
Earn continuing education credits/units! A continuing education course and exam that uses this book is also available. It may be purchased separately or as part of a package that includes all the course materials and exam.
Chapter 1. Incidence of Running-Related Injuries
Defining an Overuse Injury
Etiology of Overuse Injuries in Runners
Common Running-Related Injuries
Understanding Clinical and Biomechanical Risk Factors
Summary
Chapter 2. Assessing Foot Mechanics
Biomechanics
Atypical Foot Mechanics and Injury
Strength
Anatomical Alignment
Flexibility
Summary
Chapter 3. Footwear Selection
Overview of Running Shoes
Footwear Research Findings
Shoe Fitting
Barefoot Running
Orthotic Devices and Foot Mechanics
Summary
Chapter 4. Assessing Knee Mechanics
Biomechanics
Strength
Anatomical Alignment
Flexibility
Summary
Chapter 5. Assessing Hip Mechanics
Biomechanics
Strength
Anatomical Alignment
Flexibility
Summary
Chapter 6. Proximal to Distal Relationships: Case Studies
Torsional Forces
Frontal Plane Mechanics
Summary
Chapter 7. Can We Influence Gait Mechanics?
Feedback
Strength Training
Revisiting the Case Studies
Summary
Chapter 8. Overview of Clinical and Biomechanical Assessment
Foot, Ankle, and Tibia
Knee
Hip
Summary
Chapter 9. Technical Aspects of Video Gait Analysis
Sampling Frequency
F-Stop and Shutter Speed
Software Options
Summary
Reed Ferber, PhD, CAT(C), ATC, is an associate professor in the faculties of kinesiology and nursing at the University of Calgary and cofounder and director of the Running Injury Clinic in Calgary, Alberta, Canada. Since 2003, he and his colleagues at the Running Injury Clinic have been among the world’s leaders in 3-D gait assessment and technology. Ferber received his PhD in biomechanics from the University of Oregon in 2001. He is a research associate for the Institute of Sport and Recreation Research in New Zealand and a certified member of the Canadian Athletic Therapists’ Association and the National Athletic Trainers’ Association. He has won several awards in teaching excellence and has authored or coauthored 43 articles appearing in Clinical Biomechanics, Gait and Posture, Clinical Journal of Sports Medicine, Journal of Sport Rehabilitation, and other publications.
Shari Macdonald, BSc, PT, MSc, has worked for over 15 years as a physical therapist specializing in the assessment and treatment of musculoskeletal injuries. She has earned postgraduate certifications in manual therapy, dry needling techniques, and sport. Shari is the chairperson for the Alberta section of Sport Physiotherapy Canada and is a national board member. Since 2009, Shari has been the clinic director at the Running Injury Clinic in Calgary, Alberta, where they specialize in assessing gait biomechanics and the treatment of running injuries. Shari earned her master of science degree in biomechanics from the University of Calgary.
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/92tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab1_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab2_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab3_Main.png
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/93tab4_Main.png
Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
http://www.humankinetics.com/AcuCustom/Sitename/DAM/118/2art_Main.png
In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
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Does barefoot running cause injuries?
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years.
Barefoot running, or running in a minimalist shoe, has received increasing attention within the popular media over the past several years. However, one must first realize that barefoot running is not new to elite runners, with Abebe Bikila winning gold in the 1960 Olympic marathon while running barefoot and Zola Budd setting the world record for the 5000 m at the 1984 Olympic games. The first research study published was in 1987 (Robbins and Hanna 1987). Since then, multiple studies have been conducted to understand the potential alterations in running mechanics when running barefoot. However, it is important to note that, to date, there is no research that either supports or refutes the injury preventative aspects of running barefoot that marketing campaigns and advertisements promote. There is only research to confirm that running barefoot is different than running shod.
While looking at the effects of running in shoes compared with running barefoot, it has been reported that running barefoot, or even running with a forefoot strike as opposed to a rearfoot strike, results in decreased stride length; increased stride rate; decreased range of motion at the ankle, knee, and hips; and a more plantar flexed ankle position at ground contact (De Wit et al. 2000; Divert et al. 2005; Lieberman et al. 2010). Moreover, Kerrigan et al. (2009) reported a 54% decrease in the hip rotational forces, a 36% decrease in knee flexion forces, and a 38% decrease in frontal plane knee forces when running barefoot compared with running in shoes.
While these results appear impressive, a closer inspection reveals that there is no clear answer about whether barefoot running is injury preventative or causative. For example, by decreasing stride length, and increasing stride rate, more steps are taken per kilometer. For the average runner running a marathon, this would result in 1,280 more steps to finish the race but only two minutes less of total foot contact time over a 3 hr, 20 min time compared to running shod. The increased numbers of steps and increased repetitions of maximum vertical loading when running barefoot (or with a forefoot strike pattern) could be injury-causative. On the other hand, 36% to 54% less force at the hip and knees for every step could be injury-preventative. Moreover, based on mechanical properties of the Achilles tendon (Konsgaard et al. 2011) and when considering that a forefoot strike pattern forces the heel downwards shortly after contact with the ground (Kerrigan et al. 2009; Lieberman et al. 2010), each step taken when running barefoot results in 59% of the force needed to rupture the Achilles tendon. The increased tensile loading of the Achilles tendon could result in tendinopathy, a gastrocnemius, or soleus muscle strain.
In summary, while research has been done on how barefoot running alters an individual's mechanical patterns and joint loading, no studies have been conducted on whether injury rates or specific injuries are reduced compared with shod running. Considering the complexity of the etiology of running injuries, changing one parameter such as footwear or even eliminating shoes altogether and completely altering the mechanical pattern cannot eliminate the occurrence or potential for musculoskeletal injuries. In fact, rapid alterations in one kinematic running pattern place a runner at risk for injury. Finally, considering that the magnitude of force applied to the system, a runner's mass, does not substantially change whether barefoot or shod, the changes in mechanics attributed to running barefoot or running with a forefoot strike would simply result in the impact force being redistributed elsewhere within the body. Thus, while barefoot running may result in a reduction of some injuries, such as to the knee and hip, we are likely to see an increase in other injuries, such as to the metatarsals, plantar fascia, and Achilles tendon. Future research will help answer these questions.
Training variables for running can lead to overuse injuries
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits.
The training variables most often identified as risk factors for overuse running injuries include running distance, training intensity, rapid increases in weekly running distance or intensity, and stretching habits (James, Bates et al. 1978; Jacobs and Berson 1986; Marti et al. 1988; Messier and Pittala 1988; Paty 1994; James 1998; Plastarasv et al. 2005). Examining how these variables affect the stress-frequency relationship reveals how some of these training variables may lead to overuse injuries (figure 1.1). Increasing running distance increases the number of repetitions of the applied stress since the number of steps taken increases. Provided that running speed remained unchanged, the magnitude of the forces and moments produced at various musculoskeletal structures during each step remain unchanged also (neglecting fatigue effects). Thus, running a greater distance places the involved musculoskeletal structures further to the right on the graph by increasing the number of stress applications. Since this portion of the curve has a slight negative slope, locations further to the right on the curve require slightly lower stresses for a structure to enter the injury zone of the curve. Thus, the possibility that one or more structures will enter the injury zone of the graph increases with increasing running distance.
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In running, training intensity relates to running speed. Faster running speeds generally produce greater forces and torsional stress to the involved musculoskeletal structures (Hamill et al. 1982; Nigg 1986; Derrick et al. 2000; Mercer et al. 2002). When training intensity increases, the stress level applied to all of these structures occurs higher on the stress-frequency graph (figure 1.1). Locations higher on this graph require fewer repetitions for a structure to enter the injury zone. In this way, when training intensity increases without a decrease in running distance or frequency, the likelihood of injury also increases.
The stress-frequency relationship can also explain how rapid changes in distance or intensity increase the risk of injury. When a musculoskeletal structure is subjected to a stress-frequency combination that is close to the stress-frequency curve yet below or to the left of the curve, positive remodeling of the structure may occur, shifting the curve upward and to the right as long as detraining does not occur. When these increases in running distance and intensity are gradual, it is possible to shift the stress-frequency curve to outpace the shifting of the structure's location on the graph. However, rapid increases in running distance or intensity may cause the structure to cross the curve from the non-injury region to the injury region even when some positive remodeling and shifting of the curve has occurred.
Performing stretching exercises before running is a training-related variable that has been examined as a possible risk factor for running injuries. Unfortunately, there have been conflicting conclusions drawn regarding the association of this factor with overuse running injuries. A number of researchers have reported that people who stretch regularly before running experience a higher rate of injury than those who do not stretch regularly (Jacobs and Berson 1986; Hart et al. 1989; Rochcongar et al. 1995). On the other hand, others have not found an association between stretching before running and injuries (Blair et al.1987; Macera et al. 1989; Hreljac et al. 2000). No empirical studies have reported that regular stretching before running reduces the number of running injuries, even though this practice has been advocated as a means of preventing running injuries (van Mechelen et al. 1993). However, data related to the stretching and warm-up habits of runners generally rely on surveys or self-reporting, so these results must be considered cautiously. Indeed, it is very possible that stretching before running is important for some runners, while it may not be necessary for others. A systematic review and meta-analysis by Yeung and Yeung (2001) reported that research investigating protocols of stretching before exercise and stretching outside the training sessions did not produce a clinically useful or statistically significant reduction in the risk of soft tissue running-related injuries. Without conclusive evidence, other factors, such as training errors, should be considered first as potential contributors to injury.
Several clinical studies have estimated that over 60% of overuse running injuries are a result of variables related to training (Clement et al. 1981; Lysholm and Wiklander 1987; Kibler 1990; Macintyre et al. 1991). From a practical standpoint, it could be stated that all overuse running injuries are attributable to training variables. To sustain an overuse injury, a runner must have subjected some musculoskeletal structure to a stress-frequency combination that crossed over to the injury zone of the current stress-frequency curve for the injured structure. This can only be accomplished when an individual exceeds the current limit of running distance or intensity in such a way that the negative remodeling of the injured structure predominates over the repair process. The exact location of this limit would vary from structure to structure and from individual to individual, but there is no doubt that runners can prevent these injuries by training differently based on individual limitations or in some cases by not training at all.
One of the most appealing aspects of assigning the causes of all overuse running injuries to training variables is that all of these injuries could then be considered preventable, since runners have control over training variables. However, rarely do runners know that they are about to commit a training error that will place them outside of their injury threshold. Therefore, to prevent overuse running injuries and assess and understand the etiology of a current injury, knowledge of the current limits of all of the involved musculoskeletal structures is required. These limits primarily are determined by anatomical and biomechanical variables in addition to the current state of training, strength and flexibility of specific tissues and muscles, and the integrity and injury status of various structures. Of course, it is not possible to know these limits exactly, but it is possible to minimize the risk of injury by thoroughly understanding the key clinical and biomechanical risk factors.
This book provides clinicians with a thorough and scientifically grounded basis so that they can make evidence-based decisions about these clinical and biomechanical factors. With this in mind, we discuss the most common running injuries and their multifactorial nature based on the current research.
Road map to understanding patients and their associated pathomechanics
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity.
Now that we have discussed many interrelationships among various clinical and biomechanical factors, we hope you are gaining an appreciation for the complexity of comprehensive analysis of the entire lower extremity. In an attempt to simplify the process of establishing these interrelationships, this chapter provides several tables that show how these factors relate to one another. We call the collection of tables our road map because we constantly refer to them to help guide us through interpreting and understanding our patients and their associated pathomechanics.
We have chosen to use observable or measurable biomechanical factors as the frame of reference to help guide and assist in musculoskeletal injury assessment. Moreover, the anatomical alignment, strength, and flexibility factors discussed directly relate to those in earlier chapters. If, for example, we do not list any flexibility factors, it is because there is no literature to validate its relationship to the biomechanical variables discussed. For other variables, such as peak knee flexion, there are no anatomical alignment factors related which we can discuss. This is either because there is little or no research or because we consider it to be a nonfactor in determining the overall movement pattern. First, we start with the foot and move up the kinematic chain.
Foot, Ankle, and Tibia
For the foot, ankle, and tibia, we have listed those structural, strength, and flexibility factors we discussed in the previous chapters. These are grouped into tables by biomechanical pattern. Not all factors listed in the right-hand column will be present for any given person with that atypical movement pattern. Excessive and reduced peak rearfoot eversion are listed as both being associated with injury. Excessive peak eversion velocity and excessive time to peak rearfoot eversion are also listed, but we do not discuss reduced eversion velocity or reduced (early) time to peak eversion as there is nothing in the scientific literature. We do not consider a low eversion velocity movement to be potentially injurious either. Finally, we've listed those factors associated with excessive and reduced peak tibial internal rotation, and it should become clear how proximal biomechanical factors are associated with these motions.
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