A Dissertation Entitled Analysis of Biomechanical and Clinical Factors

A Dissertation

entitled

Analysis of Biomechanical and Clinical Factors Influencing Running Related Musculoskeletal

Injuries

Megan Quinlevan Beard

Submitted to the Graduate Faculty as partial fulfillment of the requirements for the

Doctor of Philosophy Degree in Exercise Science

______Dr. Barry Scheuermann, Committee Chair

______Dr. Phillip Gribble, Committee Member

______Dr. Luke Donovan, Committee Member

______Dr. Abbey Thomas, Committee Member

______Dr. David Bazett-Jones, Committee Member

______Dr. Patricia R. Komuniecki, Dean College of Graduate Studies

The University of Toledo

May 2015

This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of

Analysis of Biomechanical and Clinical Factors Influencing Running Related Musculoskeletal Injuries

Megan Quinlevan Beard

Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Exercise Science

The University of Toledo May 2015

Purpose: The primary purpose was to compare baseline running biomechanics of the hip, pelvis, and trunk, isometric hip strength, and trunk endurance between female runners who sustain a running related musculoskeletal injury (RRMI) during a “marathon in training” program and runners who remain injury-free (INJF). The secondary purpose was to establish the relationship of frontal plane trunk, pelvis and hip running biomechanics to isometric hip strength and trunk endurance. Methods: Fifty female runners were tested prior to starting the training program. Three-dimensional kinematics and kinetics were collected while running over ground at a self-selected speed. Kinematic variables of interest were hip, pelvic, and trunk frontal plane angles and hip transverse plane angles during the stance phase of running. Maximum isometric voluntary contractions in hip abduction, external rotation, extension and flexion were performed and reported as torque normalized to mass (Nm/kg). Additionally, trunk flexion endurance was tested by performing as many curl-ups to fatigue and was reported as the number of successful repetitions. While extension, and lateral trunk flexion endurance tests were performed suspended off a platform and held until fatigued, and reported in

iii seconds. Results: The RRMI group exhibited increased contralateral pelvic drop and ipsilateral trunk lean during the stance phase of running compared to the INJF group.

There were no significant differences for all isometric hip strength tests and trunk endurance tests between the RRMI and INJF groups. Contralateral pelvic drop was weakly correlated with isometric hip abduction strength and trunk extension endurance, and ipsilateral trunk lean was negatively correlated with lateral trunk flexion endurance.

There were no correlations between peak hip adduction during running and the strength and endurance variables. Conclusion: Faulty running mechanics, including increased contralateral pelvic drop and trunk lean, may be related to the development of a RRMI amongst female runners during training. The decreased contralateral pelvic drop exhibited during running is impacted by the trunk extensors and hip abductors.

Additionally, an increase in ipsilateral trunk lean during running was associated with decreased lateral trunk flexion strength. These results suggest the assessment of both the hip and trunk musculature and running biomechanics in the evaluation and treatment of

RRMIs. Clinicians and researchers should utilize gait analysis to identify faulty running biomechanics in runners prior to the initiation of a running regimen. Prevention strategies such as gait reeducation and strengthening to minimize frontal plane pelvic motion during running should be performed in runners who exhibit abnormal running biomechanics.

Acknowledgements

There are a number of people without whom this dissertation would not have been completed, and to whom I am greatly indebted. To my husband Tim, for your unwavering love, support and encouragement over the past several years; I am truly thankful to have you in my life. I anxiously await our new start in Columbus, Ohio this fall and all of the adventures it will bring. To my parents Pat and Karen, for your unwavering and unconditional love, for the sacrifices you made to help me get through

12 years of college, and for always answering the phone when I call, no matter the time of day; I look forward to many more phone conversations. Party on Wayne. To my siblings Mallory, Conor, Shannon, and Kayla, I am thankful for your love and encouragement. Thank you for all of the letters, care packages, and banana bread you sent over the years we were apart. To my advisor Dr. Gribble, for providing me guidance over the past four years. Your continual dedication to your students, scholarship and profession were inspiration for my own teaching and work. To my committee members, Dr. Donovan, Dr. Bazett-Jones, Dr. Thomas, and Dr. Scheuermann, I am grateful for your assistance and recommendations with my dissertation. Lastly, I cannot forget my peers, Hayley, Adam, Masa, Shinbo and Jake, and the students that assisted me with my research, Sam, Lauren, Aya, Danielle, Larry, Steven, Josh, Dylan, Steve, and

Joshua, your support and hard work is valued tremendously.

Table of Contents

Acknowledgements ...... v

List of Figures ...... xii

List of Abbreviations ...... xiv

1. Introduction ...... 1

1.1 Statement of the Problem ...... 1

1.2 Research Questions ...... 5

1.3 Hypotheses ...... 5

1.4 Assumptions ...... 6

1.5 Limitations ...... 6

1.6 Significance of the Study ...... 7

1.7 References ...... 8

2. Literature Review...... 11

2.1 Introduction ...... 11

2.2 Running Participation and Health Benefits ...... 12

2.2.1 Overall Health ...... 16

2.2.2 Running and Osteoarthritis ...... 20

2.2.3 Psychosocial Factors of Running ...... 22

2.3 Running Biomechanics ...... 26

2.3.1 Running Phases...... 26

2.3.2 Running Kinematics ...... 28

2.3.3 Foot Strike Patterns ...... 32

2.3.4 Muscle Activation Patterns during Running ...... 34

2.3.5 Ground Reaction Forces during Running ...... 37

2.3.6 Center of Pressuring during Running ...... 38

2.4 Running Related Injuries ...... 38

2.4.1 Epidemiology or RRIs ...... 38

2.4.2 Definition of a RRI ...... 39

2.4.3 Rates of RRIs ...... 41

2.4.4 Specific Diagnoses/Types of RRIs ...... 46

2.4.5 Risk Factors for RRMIs ...... 50

2.4.6 Variables Associated with Specific RRMIs ...... 59

2.5 Conclusion ...... 70

2.6 Research Line ...... 71

2.6.1 Overall Goal ...... 71

2.6.2 Alternative Goal ...... 71

2.7 References ...... 72

2.8 Tables ...... 88

2.9 Figures ...... 90

3. Running Biomechanics in Injured and Injury Free Runners Participating in a

“Marathon in Training” Program: A Prospective Cohort Study ...... 93

3.1 Abstract ...... 93

3.2 Introduction ...... 94

vii

3.3 Methods ...... 97

3.3.1 Study Design...... 97

3.3.2 Participants ...... 97

3.3.3 Instrumentation ...... 98

3.3.4 Procedures ...... 98

3.3.5 “Marathon in Training” Program ...... 99

3.3.6 Injury Tracking ...... 100

3.3.7 Data Processing ...... 101

3.3.8 Statistical Analysis ...... 102

3.4 Results ...... 102

3.4.1 Running Related Musculoskeletal Injuries ...... 102

3.4.2 Running Biomechanics ...... 103

3.5 Discussion ...... 103

3.6 Conclusion ...... 108

3.7 References ...... 109

3.8 Tables ...... 113

3.9 Figures ...... 114

4. Hip Strength and Trunk Endurance in Injured and Injury Free Runners Participating in a “Marathon in Training” Program: A Prospective Cohort Study ...... 118

4.1 Abstract ...... 118

4.2 Introduction ...... 119

4.3 Methods ...... 122

4.3.1 Study Design...... 122

4.3.2 Participants ...... 123

viii

4.3.3 Instrumentation ...... 123

4.3.4 Procedures ...... 124

4.3.5 “Marathon in Training” Program ...... 127

4.3.6 Injury Tracking ...... 127

4.3.7 Data Processing ...... 128

4.3.8 Statistical Analysis ...... 129

4.4 Results ...... 129

4.4.1 Running Related Musculoskeletal Injuries ...... 129

4.4.2 Hip Strength and Core Endurance ...... 130

4.5 Discussion ...... 130

4.6 Conclusion ...... 134

4.7 References ...... 135

4.8 Tables ...... 139

4.9 Figures ...... 142

5. Relationship between Hip Strength, Core Endurance, and Trunk, Pelvic and Hip

Kinematics during Running in Injured and Injury Free Runners ...... 146

5.1 Abstract ...... 146

5.2 Introduction ...... 147

5.3 Methods ...... 150

5.3.1 Study Design...... 150

5.3.2 Participants ...... 150

5.3.3 Instrumentation ...... 151

5.3.4 Procedures ...... 151

5.3.5 Data Processing ...... 156

5.3.6 Statistical Analysis ...... 157

5.4 Results ...... 157

5.5 Discussion ...... 158

5.6 Conclusion ...... 161

5.7 References ...... 162

5.8 Tables ...... 166

5.9 Figures ...... 169

References ...... 175

Appendices ...... 197

A. IRB Informed Consent Form ...... 197

B. Previous History Questionnaire ...... 206

C. Previous and Current Physical Activity Questionnaire ...... 209

D. Running and Social Dynamics Questionnaire ...... 211

E. Commitment to Running Scale ...... 216

F. State of Mind During Running Scale...... 217

G. New Running Related Musculoskeletal Injury Form ...... 218

List of Tables

2.1 Running related injury rates by anatomical site ...... 88

2.2 Top five specific running-related injury diagnoses ...... 89

3.1 Participant demographics ...... 113

4.1 Participant demographics ...... 139

4.2 Group comparisons between runners with a running related musculoskeletal

injury and injury free runners for isometric hip strength ...... 140

4.3 Group comparisons between runners with a running related musculoskeletal

injury and injury free runners for trunk endurance ...... 141

5.1 Participant demographics ...... 166

5.2 Group descriptive statistics ...... 167

5.3 Correlations (r) between strength and endurance, and running kinematic

variables ...... 168

List of Figures

2-1 Participation across various physical activities ...... 90

2-2 U.S. running event finishers...... 91

2-3 Finishers in U.S running events in 2012 ...... 91

2-4 Participation across various physical activities ...... 92

3-1 Frontal plane pelvic kinematics during the stance phase of running ...... 114

3-2 Frontal plane trunk kinematics during the stance phase of running ...... 115

3-3 Frontal plane hip kinematics during the stance phase of running ...... 116

3-4 Transverse plane hip kinematics during the stance phase of running ...... 117

4-1 Hip abduction strength test ...... 142

4-2 Hip external rotation strength test ...... 142

4-3 Hip extension strength test ...... 143

4-4 Hip flexion strength test ...... 143

4-5 Trunk flexor endurance test ...... 144

4-6 Trunk extensor endurance test ...... 145

4-7 Lateral trunk flexor endurance test ...... 145

5-1 Hip abduction strength test ...... 169

5-2 Hip external rotation strength test ...... 169

5-3 Hip extension strength test ...... 170

5-4 Trunk flexor endurance test ...... 171

xii

5-5 Trunk extensor endurance test ...... 172

5-6 Lateral trunk flexor endurance test ...... 172

5-7 Peak contralateral pelvic drop vs. trunk extensor endurance ...... 173

5-8 Peak contralateral pelvic drop vs. isometric hip abduction strength ...... 173

5-9 Peak ipsilateral trunk flexion vs. lateral trunk flexion endurance ...... 174

xiii

List of Abbreviations

ABC ...... Abdominal body circumference ASIS ...... Anterior superior iliac spine

BMI ...... Body mass index

CI...... Confidence interval COP ...... Center of pressure CR ...... Commitment to running

FFS ...... Forefoot strike

GRF ...... Ground reaction force GTP ...... Group training program

HABD ...... Hip abduction HDL ...... High density lipoprotein HEXR ...... Hip external rotation HEXT ...... Hip extension HFLX ...... Hip flexion HHD ...... Hand-held dynamometer

INJF...... Injury free ITB ...... Iliotibial band ITBS ...... Iliotibial band syndrome

LTFLX ...... Lateral trunk flexion

MFS...... Midfoot strike MTSS ...... Medial tibial stress syndrome

OA ...... Osteoarthritis

PFDS ...... Patellofemoral dysfunction syndrome PFP ...... Patellofemoral pain PSIS...... Posterior superior iliac spine

xiv

QL ...... Quadratus lumborum muscle

RFS ...... Rearfoot strike ROM ...... Range of motion RRCA ...... Road Runners Club of America RRI ...... Running related injury RRMI ...... Running related musculoskeletal injury

TEXT ...... Trunk extension TFLX...... Trunk flexion THM ...... Time between heel and metatarsal peak acceleration TSFX ...... Tibial stress fracture vGRF ...... Vertical ground reaction force

WHO ...... World Health Organization

Chapter 1

Introduction

1.1 Statement of the Problem

Over half of all Americans are considered inactive or insufficiently active.(WHO,

2010) Today, physical inactivity is the 4th leading risk factor for mortality in the world, accounting for approximately 3.2 million deaths across the globe.(WHO, 2009)

Additionally, physical inactivity can lead to several comorbidities such as heart disease, cancer and type two diabetes.(WHO, 2009) Fortunately, for individuals participating in running they may deter such comorbidities. Running has been associated with decreased risk for sustaining a stroke,(Williams, 2009b) and development of hypertension.(Williams, 2009a) Compared with other forms of physical activity running significantly reduced body mass index (BMI) and abdominal body circumference (ABC) at a greater rate.(Williams, 2012) This is critical as both BMI and ABC are highly associated with an increased risk for coronary heart disease, hypertension, diabetes, and high cholesterol.(Williams, Hoffman, & La, 2007; Williams & Hoffman, 2009)

Fortunately, more Americans are discovering running through events such as the

Color Run, Tough Mudder and the challenging half and full marathons. Approximately

51 million Americans participated in running or jogging in 2012, approximately 45% more than other individual and team sports.(USA, 2013) The number of finishers in running events has increased two fold from 1990 to 2012, topping off at 15.5 million finishers.(RunningUSA, 2012) Concurrent with the growth of races and finishers is a rise in the number of running clubs and group training programs (GTP). Runners participate in GTPs as a means to prepare for an event such as a half or full marathon, while deriving social and personal benefits, and hoping to minimize injury through a well-structured program.(Parker, Weitzenberg, Amey, & Nied, 2011)

Despite all the health benefits of running, and despite the GTPs aimed at minimizing the risk of sustaining an injury, up to 80% of runners will sustain a running related musculoskeletal injury (RRMI) annually.(van Gent et al., 2007) Additionally, runners with a history of a previous RRMI are up to seven times more likely to sustain an ancillary RRMI.(Macera, Pate, Woods, Davis, & Jackson, 1991) Risk factors for RRMIs have undergone limited investigated, focusing on demographics such as age, gender and weight, as well as training related factors such as weekly mileage, days ran per week, and years of running experience.(van Gent et al., 2007) Few studies have investigated musculoskeletal factors, including only static alignment factors such as arch height and leg length differences.(Lun, Meeuwisse, Stergiou, & Stefanyshyn, 2004; Wen, Puffer, &

Schmalzried, 1998) Researchers have yet to utilize active musculoskeletal factors such as muscular strength, core endurance and running biomechanics to determine risk of sustaining any type of RRMI.

According to the kinetic chain model, alterations proximally, such as at the hip joint, can result in compensations distally, further resulting in injury from abnormal

2 stresses. Researchers investigating individual RRMIs such as patellofemoral pain (PFP), iliotibial band syndrome (ITBS), medial tibial stress syndrome (MTSS) and tibial stress fractures (TSFX) have examined the role of hip strength and altered lumbo-pelvic-hip running kinematics in injured and healthy individuals. Although these four specific diagnoses make up almost 38% percent of all RRMIs, limited investigations have included runners.(Taunton et al., 2002) Those investigations including runners, have found decreased hip abduction strength,(Dierks & Davis, 2008; Fredericson et al., 2000) and external rotation strength,(Noehren, Schmitz, Hempel, Westlake, & Black, 2014) as well as increased hip adduction,(Ferber, Noehren, Hamill, & Davis, 2010; Noehren, Pohl,

Sanchez, Cunningham, & Lattermann, 2012) internal rotation,(Loudon & Reiman, 2012;

Noehren et al., 2012) and contralateral pelvic drop running kinematics.(Loudon &

Reiman, 2012) Increased contralateral pelvic drop during running is a sign of core instability. The hip musculature is not the only musculature involved in stabilizing the core, the trunk flexors, extensors and lateral flexors also provide a crucial role. Leetun and colleagues compared trunk endurance and hip strength amongst collegiate male and female, basketball and cross country athletes that sustained an injury during season and those that remained injury free.(Leetun, Ireland, Willson, Ballantyne, & Davis, 2004) The authors identified no prospective differences on the side bridge and trunk extension tests between injured and injury free athletes. Interpretation of the results should be taken lightly as they grouped males and females together, as well as two different athletic populations. Basketball and cross country are two different sports, with basketball requiring more side-to-side movement, while competitive running demands repetitive,

3 sagittal plane lower extremity motion. Thus the demand on the core musculature during these activities would also differ.

The studies demonstrating strength deficits and kinematic alterations during running have been mostly limited to retrospective studies. Less than a handful of studies have been conducted prospectively and are limited to individual populations of RRMIs.

Only two studies have investigated prospectively running kinematics as a predisposing factor for PFP (Noehren, Hamill, & Davis, 2013) and ITBS.(Noehren, Davis, & Hamill,

2007) The authors mutually reported that increased hip adduction during running was observed at baseline in runners who developed PFP and ITBS compared to runners who remained injury free. Thus, the development of PFP and ITBS appears to be related to transformed running mechanics. The same was not found for the prospective association between hip strength and the development of PFP.(Thijs, Pattyn, Van Tiggelen, Rombaut,

& Witvrouw, 2011) Runners who developed PFP did not exhibit different hip abduction, adduction, flexion, extension, internal rotation and external rotation strength compared to runners who remained injury free during a training program. Thus, perhaps unlike running mechanics, hip strength deficits are the result of the injury rather than a predisposing factor for injury. However, these studies are limited to their specific populations of RRMIs; therefore, prospective examination into kinematic alterations and strength deficits for runners with all types of RRMIs is warranted.

1.2 Research Questions

1. Are there differences in baseline running biomechanics between runners who

sustain an RRMI during training and runners who remain injury free?

2. Are there differences in baseline isometric hip strength and trunk endurance

between runners who sustain an RRMI during training and runners who remain injury

free?

3. Is there a relationship between frontal plane running biomechanics, isometric hip

strength and trunk endurance amongst female runners?

1.3 Hypotheses

1. Female runners that sustain an RRMI during training will exhibit increased frontal

plane trunk, pelvis, and hip kinematics, and transverse plane hip kinematics during

the stance phase of running compared to females who remain injury free during

training.

2. Female runners that sustain an RRMI during training will exhibit decreased

isometric hip abduction, external rotation, extension and flexion strength, as well as

decreased trunk flexor, extensor and lateral flexor endurance compared to females

who remain injury free during training.

3. There will be a strong correlation between frontal plane running kinematics at the

hip, pelvis and trunk, with hip abduction and lateral trunk flexor endurance amongst

female runners.

1.4 Assumptions

 All participants will be honest when completing running and injury history

questionnaires

 All measurement tools will be used accurately and responsibly to assess

participants

 All participants will give their best effort during the baseline testing session

 All participants will run normally during the 3D motion analysis

 All participants will perform maximum effort during strength, and endurance

testing

 All participants will report injuries as they occur, and honestly describe their

injury and symptoms

1.5 Limitations

 Sample size was one of convenience

 Multiple injuries were assessed

 Only collected females, thus not generalizable to males

 Post injury session was not performed to evaluate pre-post injury mechanics and

strength

1.6 Significance of the Study

Due to an increase in participation in running and the concomitant increase in running related musculoskeletal injuries (RRMI), it is important to identify predisposing factors that could place female runners at risk for an RRMI. Running biomechanics could play an important part in the development of an injury, whereas decreases in hip strength and core endurance could be the result of the injury. A weak association exists between hip strength, core endurance, and running biomechanics, suggesting the need to investigate other factors such as neuromuscular control. An orthopedic exam should be performed for both runners who are interested in training and those that are already injured. Included in the exam should be a running gait analysis as well as hip strength and core endurance testing, and based on the results, appropriate interventions strategies should be implemented.

1.7 References

Dierks, T. A., & Davis, I. (2008). Lower extremity alignment and knee valgus during

prolonged running in runners with patellofemoral pain. Med Sci Sports Exerc,

40(5), S339-S340.

Ferber, R., Noehren, B., Hamill, J., & Davis, I. (2010). Competitive female runners with

a history of iliotibial band syndrome demonstrate atypical hip and knee

kinematics. J Orthop Sports Phys Ther, 40(2), 52-58.

Fredericson, M., Cookingham, C. L., Chaudhari, A. M., Dowdell, B. C., Oestreicher, N.,

& Sahrmann, S. A. (2000). Hip abductor weakness in distance runners with

iliotibial band syndrome. Clin J Sport Med, 10(3), 169-175.

Leetun, D. T., Ireland, M. L., Willson, J. D., Ballantyne, B. T., & Davis, I. (2004). Core

stability measures as risk factors for lower extremity injury in athletes. Med Sci

Sports Exerc, 36(6), 926-934.

Loudon, J. K., & Reiman, M. P. (2012). Lower extremity kinematics in running athletes

with and without a history of medial shin pain. Int J Sports Phys Ther, 7(4), 356-

364.

Lun, V., Meeuwisse, W., Stergiou, P., & Stefanyshyn, D. (2004). Relation between

running injury and static lower limb alignment in recreational runners. Br J Sports

Med, 38(5), 576-580.

Macera, C. A., Pate, R. R., Woods, J., Davis, D. R., & Jackson, K. L. (1991). Postrace

morbidity among runners. Am J Prev Med, 7(4), 194-198.

Noehren, B., Hamill, J., & Davis, I. (2013). Prospective evidence for a hip etiology in

patellofemoral pain. Med Sci Sport Exer, 45(6), 1120-1124. 8

Noehren, B., Pohl, M. B., Sanchez, Z., Cunningham, T., & Lattermann, C. (2012).

Proximal and distal kinematics in female runners with patellofemoral pain. Clin

Biomech, 27(4), 366-371.

Noehren, Schmitz, A., Hempel, R., Westlake, C., & Black, W. (2014). Assessment of

strength, flexibility, and running mechanics in men with iliotibial band syndrome.

J Orthop Sport Phys, 44(3), 217-222.

Noehren, B., Davis, I., & Hamill, J. (2007). Prospective study of the biomechanical

factors associated with iliotibial band syndrome. Clin Biomech, 22(9), 951-956.

Parker, D. T., Weitzenberg, T. W., Amey, A. L., & Nied, R. J. (2011). Group training

programs and self-reported injury risk in female marathoners. Clin J Sport Med,

21(6), 499-507.

RunningUSA. (2012). 2012 State of the Sport Part II: Running Industry Report.

Retrieved January 26, 2012, from http://www.runningusa.org/statistics.

Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R., &

Zumbo, B. D. (2002). A retrospective case-control injuries analysis of 2002

running. Br J Sports Med, 36(2), 95-101.

Thijs, Y., Pattyn, E., Van Tiggelen, D., Rombaut, L., & Witvrouw, E. (2011). Is hip

muscle weakness a predisposing factor for patellofemoral pain in female novice

runners? A prospective study. Am J Sports Med, 39(9), 1877-1882.

USA, S. M. S. (2013). 2013 Participation Report (P. A. Council, Trans.) (2013 ed., pp.

15). van Gent, R. N., Siem, D., van Middelkoop, M., van Os, A. G., Bierma-Zeinstra, S. M.,

& Koes, B. W. (2007). Incidence and determinants of lower extremity running

injuries in long distance runners: a systematic review. Br J Sports Med, 41(8),

469-480.

Wen, D. Y., Puffer, J. C., & Schmalzried, T. P. (1998). Injuries in runners: a prospective

study of alignment. Clin J Sport Med, 8(3), 187-194.

WHO. (2009). Global health risks: mortality and burden of disease attributable to

selected major risks. (9241563877). World Health Organization.

WHO. (2010). Global recommendations on physical activity for health. World Health

Organization.

Williams, P. T. (2009a). Lower prevalence of hypertension, hypercholesterolemia, and

diabetes in marathoners. Med Sci Sports Exerc, 41(3), 523.

Williams, P. T. (2009b). Reduction in incident stroke risk with vigorous physical activity

evidence from 7.7-year follow-up of the national runners’ health study. Stroke,

40(5), 1921-1923.

Williams, P. T. (2012). Non-exchangeability of running vs. other exercise in their

association with adiposity, and its implications for public health

recommendations. Plos One, 7(7), e36360.

Williams, P. T., Hoffman, K., & La, I. (2007). Weight-related increases in hypertension,

hypercholesterolemia, and diabetes risk in normal weight male and female

runners. Arterioscler Thromb Vasc Biol, 27(8), 1811-1819.

Williams, P. T., & Hoffman, K. M. (2009). Optimal body weight for the prevention of

coronary heart disease in normal‐weight physically active men. Obesity, 17(7),

1428-1434.

Chapter 2

Literature Review

2.1 Introduction

For more than four decades the sport of running has consistently been reported to improve and maintain both physical health and emotional well-being.(Jorgenson &

Jorgenson, 1979; Williams & Thompson, 2013) Concurrently, over the past decade the number of annual running participants has increased drastically from almost 36 million to over 51 million Americans.(RunningUSA, 2013b) Hence running is an avenue more and more Americans choose as their form of physical activity to stay in shape, stay healthy, relieve stress, and have fun.(RunningUSA, 2013a) Unfortunately, a consequence of running is that up to 80% of runners may sustain a running-related musculoskeletal injury

(RRMI).(Fredericson & Misra, 2007; van Gent et al., 2007; Van Middelkoop, Kolkman,

Van Ochten, Bierma-Zeinstra, & Koes, 2008) Likewise, runners that have sustained a

RRMI are up to five times more likely to sustain another injury.(Parker, Weitzenberg,

Amey, & Nied, 2011)

Temporary or permanent inactivity following injury could conceivably result in weight gain, depression, and a permanent halt to physical activity further leading to the

11 likely development of several severe co-morbidities.(Chan & Grossman, 1988; Ezzati et al., 2003; King et al., 2001) Persons that are physically inactive are 50% more likely to become obese,(King et al., 2001) and are at a substantially greater risk for sustaining a cerebrovascular accident or developing ischemic heart disease.(Ezzati et al., 2003) For that reason, it is of the upmost importance to keep individuals participating in physical activities such as running as it is easy to implement, time effective, has minimal associated costs, and can provide a range of physical and psychological health benefits.

Presently, it is essential to perform an inclusive investigation into the epidemiology, etiology and pathophysiology of RRMIs, as well as the participation rates of running programs and races, the health benefits of running, and current musculoskeletal assessments tools used to detect persons at risk of an injury in order to develop avenues for prevention of RRMIs.

2.2 Running Participation and Health Benefits

Across the United States in 2012, it was estimated that approximately 51.5 million

Americans participated in running or jogging within the preceding year.(USA, 2013)

Over the past half-decade the number of Americans choosing to participate as both casual

(1 to 49 times per year) and frequent (100+ times per year) runners has increased by 27% and 19% respectively.(USA, 2012) Compared with other forms of physical activity including fitness sports (elliptical motion trainer, aerobic exercise and stationary cycling) and team sports (basketball, football and soccer), running/jogging has 45% more participants than any of these physical activities (Figure 2-1).(USA, 2012)

Coinciding with an increase in the number of leisurely runners, there has also been an upsurge in the number of participants registering for running events/races.(RunningUSA, 2013b) In 1990, the number of running event finishers was just shy of 5 million Americans, with 25% female and the remaining 75% male finishers.

Fast forward to 2012 and there were 15.5 million finishers in running events/races overall, a 224% increase over 22 years. Additionally in 2012, the number of female finishers reached a record high at about 8.6 million Americans, accounting for 56% of finishers, while the number of male finishers also attained an all-time high with 6.8 million Americans, 44% of all finishers (Figure 2-2).

The four most popular races in the United States are the 5K (3.1miles), 10K (6.2 miles), half-marathon (13.1miles), and marathon (26.2 miles; Figure 2-3).(RunningUSA,

2013b) In 2012, the 5K race distance was the number one event with over 6.2 million

American finishers, almost an 18% increase from 2011. Charities in particular have benefitted from the 5K events and have seen a significant increase in contributions to their organizations. In 2012, 30 charities across the United States hosted over 35,000 5K events and raised over 1.68 billion dollars. The traditional road 5K has seen many changes over the past years with the edition of The Color Run, Foam Fest, and Zombie

Run. Also emerging across the nation are several non-traditional 5K events such as the

Tough Mudder, and Warrior Dash. These events bring in all levels of runners and athletes who find these events an attractive way to be active, yet not competitive.

Over the past 10 years, the half-marathon has become the fastest growing road race in the United states.(RunningUSA, 2013b) In 1990, it was estimated that 303,000

Americans finished a half-marathon.(RunningUSA, 2013b) In the 1,136 half-marathon

13 events across the nation in 2012, there was a record number 1.85 million American finishers. In the past 8 years alone, there has been a growth of over 200% in American half-marathon finishers (Figure 2-3), with a rise in female participation from 53 to 60%.

The marathon event dates back to the 1896 Olympics; however now it is not just an event for elite runners, but attracts recreational runners of all ages and types. The marathon race too has seen a sharp rise in the number of runners from 1976 to 2012. For example, in

1975 the NYC marathon had only 575 entrants, but the 2013 INC NYC Marathon had

50,740 registered runners. In total, marathons across the United States have seen over half a million finishers, nineteen times the number of finishers in 1976 (about 25,000 finishers).

In addition to the growth of running events and races, more running clubs are emerging across the country. According to the Road Runners Club of America, the oldest and largest organization dedicated to distance running, there are currently 1,124 running clubs across the United States.(RRCA, 2013) Furthermore, clubs, race organizations, and companies are providing specialized group training programs (GTP) aimed at preparing runners for their designated events. Participants are enrolling in GTPs for training and race strategies, and to receive both social and personal benefits.(Parker et al., 2011)

Females have been more attracted to GTPs compared to male athletes, as well as those with less running experience.(Chorley, Cianca, Divine, & Hew, 2002) Approximately

35.6% of participants in a marathon GTP were reported to be obese, while 16.1% were sedentary the 3 months prior to starting the GTP.(Chorley et al., 2002) GTPs have been criticized for segregating runners by experience and speed, and pushing runners, specifically those with no previous training or running experience, beyond their abilities.

Yet GTP participation has been strongly associated with increased satisfaction in performance and increased likelihood to participate in future running endeavors.(Parker et al., 2011) However, it may be beneficial to establish a baseline level of fitness prior to entering a GTP and provide a variety of goal levels to accommodate runners with various levels of physical activity. Lastly, GTPs should concomitantly offer education on running technique specifically to those with minimal to zero running experience to minimize the incidence of RRMIs.

Researchers, and runners themselves, use several classifications to distinguish groups of runners. Researchers utilize theses classifications as a means of drawing comparisons amongst the wide variety, whereas runners use these terms to distinguish or identify themselves to other runners. For example, runners have been classified as beginner, intermediate, and advanced, or also as novice, recreational and competitive, both groupings being based on either experience or by race pace. However, one classification incorporates multiple components including miles per week, race history, involvement in running subculture, and reason for participation.(Robbins & Joseph,

1980) This classification is greatly beneficial when classifying recreational runners as individuals report a wide variety of reasons for choosing to participate in running. Via this classification system, runners can be classified as:

- Full-time runner: Runs more than 40 miles per week, is heavily involved in

racing, most new friends are runners, immersed in running subculture, and

running literature occupies their time weekly.

- Part-time runner: Runs 11 to 40+ miles per week, heavily involved in racing

but less involved in running subculture, competitive runners with talent that

will continually reinforce efforts at improvement

- Hobby runner: Runs 11 to 40+ miles per week, rarely races, subculture and

race performance are not important, expects no payback other than the joy of

participation.

- Occasional runner: Runs 4 to 24+ miles per week, runs at least one day per

week, running either tapers or stops during winter months.

Typical U.S. recreational, part-time female and male runner profiles have been established yearly for the past several years.(RunningUSA, 2013a) A typical part-time female runner is described as approximately 39 years of age, has about 9.5 years of running experience, and runs on average 4 days and 20 miles per week. On the other hand, the typical U.S recreational, part-time male runner is approximately 48 years old, has about 13.5 years of running experience, and runs on average 4 days and 26 miles per week.(RunningUSA, 2013a) Both the typical U.S female and male runners report their primary reason to start running as a form of exercise and for weight concerns. Once involved, motivation to keep running for both males and females is to stay in shape, stay healthy and relieve stress. Henceforward, individuals should chose to run for its substantial physical and psychological health benefits.

2.2.1 Overall Health

In 2010 the World Health Organization (WHO, 2010) provided recommendations for leisurely physical activity for children and adults: 16

- Children 5 to 17 years of age: 60 minutes of moderate or vigorous intensity

physical activity daily, with vigorous intensity physical activity at least 3

times per week, and with the majority being aerobic

- Adults 18 to 64 years of age: at least 150 minutes of moderate intensity

aerobic activity or 75 minutes of vigorous intensity aerobic activity per week,

and muscle strengthening should be performed at least twice per week.

- Adults 65 years of age or older: at least 150 minutes of moderate intensity

aerobic activity or75 minutes of vigorous intensity aerobic activity per week;

adults with poor mobility should perform physical activity to enhance balance

and prevent falls at least three days per week, muscle strengthening should be

performed at least twice per week, and adults that cannot meet the

recommendations due to health conditions should perform physical activity as

their condition permits.

According to these guidelines, it was estimated that 32% of American adults were inactive, 19% were insufficiently active, and 49% were sufficiently active in their aerobic activity level. Additionally, women were more likely to be inactive or insufficiently active compared to men for aerobic physical activity. According to the WHO, physical inactivity is the fourth leading risk factor for mortality across the globe, and responsible for an estimated 3.2 million deaths. In addition, physical inactivity is associated with the development of many diseases including heart disease, cancer, and type two diabetes.(WHO, 2009) On the reverse side, physical activity has been identified to positively reduce the risk of heart disease, stroke, diabetes, hypertension, colon and breast cancer, and depression.(WHO, 2009) 17

Running is one of the most common forms of vigorous intensity physical activity that is used to maintain a healthy lifestyle, and can improve or preserve physical and psychological health.(Summers, Machin, & Sargent, 1983) Many benefits of running have been established including enriched cardiovascular, strength, and endurance fitness,(S. Willick, 2001) improved bone density,(Wilks et al., 2009) and a positive effect on mood(Schneider et al., 2009) and cognition.(Rolland, Abellan van Kan, & Vellas,

2010) Concomitantly, running can reducing one’s risk for a stroke (Williams, 2009b) and the development of hypertension.(Williams, 2009a) The physical activity recommendations provided by the WHO presume that different intensity activities can be exchanged to receive the same health benefits, so long as the energy expenditures are equivalent when adjusting for time.(WHO, 2010)

In a research study examining the physical activity of over 33,000 runners over five years, the benefits of running significantly outweighed the benefits from other forms of physical activities. When normalized to energy expenditure per hour per day, body mass index (BMI) and abdominal body circumference (ABC) decreased at a significantly greater rate for running (BMI=0.29±0.01kg/m2 per MET*hour/day; ABC=0.067±0.02cm) compared to other combined moderate and vigorous intensity non-running physical activities (BMI=0.02±0.00kgm2 per MET*hour/day; ABC=0.10±0.01cm).(P. T.

Williams, 2012b) Researchers have revealed that a greater BMI and excess abdominal visceral fat is associated with an increase in risk for coronary heart disease, hypertension, diabetes, and high cholesterol thus running may be the most advantageous form of physical activity to thwart or deter several serious comorbidities.(Williams, Hoffman, &

La, 2007; Williams & Hoffman, 2009)

Researchers have successfully investigated the relationship of running to a substantial number of diseases and conditions.(Williams, 2012a) In a study of over

45,000 runners, individuals who ran the recommended minimum dose of aerobic physical activity (1.2 to1.9 miles per day) had a significant, positive relationship to their parent’s adiposity. However, as running distance increased the inheritance of parental adiposity to runners BMI (males: p<10-10; females: p<10-5) and waist circumference (males: P<10-9; females: P=0.004) significantly decreased. More specifically, male runners decreased their parental contribution to BMI by 29%, 39% and 48% when they ran 1.9 to 3.6, 3.7 to 5.6, or greater than 5.7 miles per day respectively. This research suggests that exceeding the minimum physical activity recommendations for running may be necessary to prevent unhealthy weight gain and confront obesity.

Several health benefits have been associated with the number of miles run per week.(Williams, 1997b) Runners who ran more than 49 miles per week (approximately 7 miles per day, per week) demonstrated an 85% reduction in the prevalence of high density lipoproteins (HDL), and a 50% reduction in both hypertension and the utilization of medication to control blood and cholesterol levels. Conversely, as runners’ mileage decreased they experienced an increase in BMI, with the steepest increase in weight gain occurring from a decrease in mileage from 5 to 0 miles per week.(Williams, 2008) Yet once running mileage increased above 10 miles per week, significant weight loss was observed. Researchers have established prospectively that running attenuates age-related weight gain, with an inverse relationship between running mileage and weight gain increases and decreases relative to a decrease and increase in running, respectively.(Williams, 2007; Williams & Wood, 2006)

Moreover, running can attenuate the intensely established relationship between diet and weight gain.(Williams, 2011) Researchers continually confirm that BMI will increase with an associated increase in meat and a decrease in fruit consumption.(Williams, 1997a, 2011) However, the relationship between food consumption and BMI can be modulated with a vigorous physical activity such as running. In men, running associates with a decrease in waist and chest circumference, and meat intake. Additionally, a decrease in chest circumference in men was inversely related to an increase in fruit consumption. In women, an increase in BMI, and chest, waist, and hip circumferences were significantly related to an increase in meat consumption within their diet. However, low mileage runners (<1.2 miles per day) had a stronger relationship between diet and BMI and body circumferences compared to high mileage runners (>3.7 miles per day). In high mileage runners, diet had a diminished effect on BMI, possibly due a more balanced coupling between energy intake and expenditure that occurs with higher levels of physical activity. As a consequence, running is not only directly related with substantial health benefits, but it further promotes additional health conscious decisions that may propagate extra health improvements.

2.2.2 Running and Osteoarthritis

Osteoarthritis (OA) is one of the leading causes of disability among adults greater than 55 years of age.(Hunter & Eckstein, 2009) OA is described as a degeneration of the articular cartilage and exposure of the underlying subchondral bone. When the degenerative joint moves, wear and tear occurs from the bone on bone contact creating pain, joint stiffness, limited motion, and localized inflammation. OA can be diagnosed by

20 radiographic findings with the identification of joint space narrowing, osteophyte formation, as well as subchondral cysts.(Lane, 1995) However, radiographic findings may not correlate to physical signs and symptoms.(Alexander, 1990; Lane et al., 1993;

Panush & Lane, 1994) Several intrinsic and extrinsic factors can prompt destruction and the downward decline in the integrity of a joint. For example, intrinsic factors include cartilage thickness, the strength of the bones contributing to the joint, muscular strength, and neuromuscular control of the joint. Influential extrinsic factors on a joint are training technique, and duration and rate of an applied force on the joint.(S. E. Willick & Hansen,

2010)

Some previous research has identified a relationship between running and the development of OA.(Cheng et al., 2000; Marti, Knobloch, Tschopp, Jucker, & Howald,

1989; McDermott & Freyne, 1983) These authors established that distance runners are at a greater risk,(McDermott & Freyne, 1983) specifically when runners increased their mileage above 20(Marti et al., 1989) or 65 miles per week.(Cheng et al., 2000) However, traumatic injuries were greater in some of the identified running populations making it difficult to draw the comparison between the running and OA.(McDermott & Freyne,

1983)

In contrast, running has been identified as unrelated to the development of OA. In two studies following runners and age-matched non-runners, there were no differences between groups in the development of OA, both with musculoskeletal and radiographic assessments.(Lane, Oehlert, Bloch, & Fries, 1998; Panush et al., 1986) In an eight year follow up of both runners and non-runners, there were no significant differences in cartilage thickness or grades of OA in the lower extremity joints between the

21 groups.(Panush et al., 1995) One exceptional study examining almost 75,000 participants found no evidence that running increased a person’s risk of OA.(Williams, 2013) On the contrary, these authors reported that participants who ran at least 8 miles per week were at a significantly lower risk for OA and hip replacement. In addition, other non-running exercises increased the risk for both OA and hip replacement compared to running. When comparing rates of OA across sports, particular at the knee complex, soccer players

(29%) and weight lifters (31%) had more than twofold the prevalence of OA compared to runners (14%).(Kujala et al., 1995) Thus, OA I to be more common in activities that require repetitive multi-planar movement, knee bending or squatting, compared to monotonous, single plane running. Recreational runners, who meet the recommend daily activity level by running, may not be at an increased risk for osteoarthritis. Future investigation into OA and running should place emphasis on runners who run above and beyond the recommend weekly levels of physical activity.

2.2.3 Psychosocial Factors of Running

Since the late 1970s when the U.S experienced its first “running boom”, researchers began investigating recreational runners’ motives and outcomes derived from both participation in running for exercise and competing in events, particularly the marathon. Both positive and negative psychological and social consequences of long distance running within recreational runners have been identified. Running can provide a meditative or altered state of consciousness,(Carmack & Martens, 1979; Henderson,

1976) which can promote an increase in mental strength, and the removal of thoughts of pain, misery, or distraught.(Glasser, 1976) Hence, running has been identified as an

22 effective therapeutic medium for the treatment of anxiety and depression.(Kostrubala,

1977) Running has shown to be just as effective in alleviating depressive symptoms when compared with timed and unlimited time sessions of psychotherapy treatment.(Greist et al., 1979) Several explanations exist for the improvement in depressive symptoms with running including mastery of a task as being perceived as difficult, the development of patience and regular consistent effort, change in physical health, appearance, and body image, and an increase in self-acceptance.(Greist et al., 1979) Running is an exceptionally natural task of rhythmic activity, which can concomitantly provide a dose of contentment and relaxation.

In addition to the positive effects of running for exercise, the task of completing a long distance marathon can provide distinctly constructive effects. After successful completion of a marathon, runners report an improvement in their ability to persevere under pressure, to obtain goals, and have a better understanding of their own capabilities and limitations.(Summers et al., 1983) However depending on a runner’s age and gender, the marathon may provide different types of achievement goals.(Maehr & Kleiber, 1981)

Younger male runners reported running a marathon to achieve a sense of competence relative to others, whereas older male runners reported a sense of mastery over one’s body despite the debilitating effects of age. Females on the other hand aim to run a marathon to gain a sense of control over their own destiny. Therefore the unique attraction of the marathon may be that it is the ideal race to accomplish a variety of achievement goals.

On the other hand, several negative consequences of running have been established. Of the upmost importance is the negative addiction runners can

23 develop.(Morgan, O'Connor, Sparling, & Pate, 1987; Robbins & Joseph, 1980) The commitment to running (CR) scale was established in 1979 to develop a reliable method for measuring level of addiction to running.(Carmack & Martens, 1979) A negative addiction to running, or those that score higher on the CR scale are characterized by(Carmack & Martens, 1979; Morgan et al., 1987; Robbins & Joseph, 1980; Summers,

Sargent, Levey, & Murray, 1982):

- a compulsive need to run at least once per day,

- run more than 40 miles per week,

- rearrange daily schedules to meet the need to run,

- experience symptoms of restlessness and guilt when a daily run is missed,

- place increased emphasis on psychological reasons for continuing to run

versus physical health reasons,

- continue to run even when injured,

- show diminished excitement in leisurely activities other than running,

- and neglect other priorities such as relationships, family, and work.

A negative addiction to running begins when a runner reorders his or her priorities. With this shift in priorities, the runner gravitates from external rewards such as success in the work place, to internal rewards of self-achievement in running.(Morgan,

1979) Once the runner places emphasis on him or herself, relationships, family, and work are now secondary obligations behind running.

Researchers observed that with a greater commitment to running brought a stronger, negative impact on relationships, family and work.(Summers et al., 1983) Forty

24 four percent of runners reported their spouses or partners complained of neglect, and 46% reported their spouses or partners always complained they were fatigued. However, runners whose spouse or partner also ran reported significantly more happiness compared to runners with non-runner spouses or partners (p<0.01). In a non-dual running relationship, the higher the CR score of the running spouse, the greater the amount of conflict. The level of conflict did not change when both persons in the relationship were runners. In the work force, runners with a higher CR scale down their occupational aspirations and transferred them to running. These same runners also admitted to fantasizing about running while at work and identified themselves first as a runner and secondly as a professional or business person.(Robbins & Joseph, 1980)

Since the late 1970s and early 1980s when the majority of articles were published on the positive and negative aspects of running, the U.S has foraged through a series of health epidemics that are forcing more individuals to start exercising. From 1990 to 2010, the number of obese children and adults in the United States escalated from 12% to

51%.(Flegal, Carroll, Ogden, & Curtin, 2010; Ogden, Carroll, Kit, & Flegal, 2014; Pan,

Blanck, Sherry, Dalenius, & Grummer-Strawn, 2012) In addition, the number of inactive individuals reached an all-time high in 2010 at 32% of Americans.(CDC, 2012) Obesity and physical inactivity are two of the top five leading global risks for mortality in the world, and are additionally responsible for raising the risk for several chronic diseases.(WHO, 2009) Hence, primary motives for running, outcomes derived from running, and level of running addiction may have changed over the past few decades warranting re-investigation.

2.3 Running Biomechanics

Running is one of the most common modes of aerobic activity performed in both individual events as well as team sports. The transition to running from walking varies between individuals but commonly occurs between 4.5 to 5.0 mph (13.33 to 12 min/mile).(Loudon, Manske, & Reiman, 2013) Compared with walking, running is characterized by a double float period when both feet are off the ground and a shortened running cycle lasting approximately 0.7 seconds, compared to 1.0 second during walking.

The double float phase contributes to a greater magnitude of ground reaction forces

(GRFs) when the foot makes impact. The magnitudes of GRFs during running are 2.0 to

6.0 times body weight during running compared to 1.0 to 1.5 times body weight during walking. With the increase in forces during running comes a necessity for increased strength and range of motion to decelerate the body and attenuate the forces at foot strike.

When the necessary strength and range of motion are not present within a runner to support the demands on the body, failure occurs resulting in injury. In order to clinically evaluate injuries associated with running, it is important to understand the phases of running, as well as joint kinematics and kinetics, and muscle activity during running.

2.3.1 Running Phases

Running gait can be separated into two distinct phases, the stance phase and the swing phase.(Loudon et al., 2013) The stance phase can further be subdivided into initial foot contact, mid support, and take-off and the swing phase can further be sectioned into follow-through, forward swing, and foot descent. Several researchers divide the stance phase into five stages compared to the traditional three, including the braking or 26 absorption phase between initial foot contact and mid support, and the propulsion phase between and mid support and take-off. The stance phase accounts for 38 to 45% of one total gait cycle, while the swing phase makes up the remaining 55 to 62%. One gait cycle is defined as the initial foot contact of one foot, to the following foot contact with the same foot.(Ounpuu, 1994)

The stance phase of running begins with initial foot contact, in which the heel, midfoot, or the forefoot, establishes contact with the ground.(Loudon et al., 2013) Once the foot plants on the ground, the absorption/braking phase begins. The subtalar joint pronates to allow the foot to adapt to the ground surface, and the ankle and knee are at maximum flexion angles while muscles are working eccentrically to assist in the absorption of GRFs and break the foreword momentum of the body. When the foot is flat on the ground the mid support phase is reached. Next the body moves forward over the stance limb with assistance from the lower extremity muscles working concentrically while the arms assist in providing an upward lift or momentum. This anterior movement represents the propulsion phase. The body is propelled forward until the foot lifts off of the ground, starting at the heel and ending with the toes. When the foot leaves the ground this signifies take off.

Immediately after take-off is the first of two double float periods in which neither foot makes contact with the ground, also marking the start of the swing phase.(Loudon et al., 2013) Once the foot leaves the ground backward momentum drives the leg posteriorly. The first phase of the swing phase is termed the follow-through and is achieved when the leg reaches its most posterior position and the knee reaches its maximum flexion angle. The limb is then reversed and muscles contract to pull the leg

27 anteriorly initiating the forward swing phase. Finally, once the limb reaches an optimal position it descends the foot to prepare for initial foot contact, also known as the foot decent phase. At the end of the foot descent phase and just prior to initial foot contact is when the second double float period occurs. Once initial foot contact occurs a new gait cycle begins and the phases repeat.

2.3.2 Running Kinematics

During running, the greatest degree of movement occurs within the sagittal plane at the trunk and lower extremity joints, with a lesser degree of movement happening in both the frontal and transverse planes. A greater range of motion occurs during running compared to walking gait. To discern movements during running it is best to analyze kinematics by each individual joint.

Trunk Kinematics. The trunk consists of the sternum, ribs, thoracic and lumbar vertebrae, and supporting ligaments and muscles. The muscles of the core help to absorb and distribute forces during impact and aid in the fluent movement of the body during running. At initial foot contact the trunk is in its most erect position.(Schache, Bennell,

Blanch, & Wrigley, 1999) Through the remainder of stance phase the trunk flexes anteriorly reaching its maximum flexion angle of 3 to 13° at take-off. Additionally, after foot contact the trunk reaches a maximum lateral flexion angle of 5 to 20°. Lateral trunk flexion is observed in coordination with pelvic drop of the side of the swing limb.

Pelvic Kinematics. At the beginning of the stance phase the sagittal plane position of the pelvis is a slight posterior tilt. As the body moves into mid support phase, the pelvis begins to rotate anteriorly, reaching maximum anterior pelvic tilt at take-

28 off.(Schache et al., 1999) As the swing phase begins the pelvis rotates slightly posteriorly, and then reverses anteriorly during foot descent. The total range of anterior/posterior pelvic tilt during one gait cycle is 10 to 15°. As speed increases, a minimal change in anterior pelvic tilt occurs. Anterior/posterior pelvic tilt range of motion greater than 15 degrees could compromise the body’s energy efficiency during running and lead to overuse injuries.(Novacheck, 1998)

Pelvic range of motion within the frontal plane is termed lateral pelvic tilt.(Loudon et al., 2013) A neutral pelvis is relatively horizontal, while contralateral pelvic tilt or drop represents when the side opposite the stance leg drops below neutral.

At foot strike the pelvis is level, but then the contralateral pelvis of the stance leg drops, reaching a maximum of 5-8 degrees at takeoff. Through swing phase the pelvis returns to neutral to assist in foot clearance from the ground.

Pelvic motion in the transverse plane is termed internal or external rotation.

Internal pelvic rotation is described as the reference side of the pelvis facing anteriorly, while external pelvic rotation is when it faces posteriorly. At initial contact the pelvis is externally rotated, and continues to externally rotate until the mid-support phase. From mid support to take off the pelvis internally rotates to a neutral position at take-off.

However, the pelvis continues to internally rotate into the swing phase reaching maximum internal rotation at midswing phase. Internal and external rotation of the pelvis offsets the rotation of the shoulders and arms, thus improving energy efficiency.(Novacheck, 1998)

Hip Kinematics. At initial foot contact the hip can be in up to 65° of flexion.(Schache et al., 1999) Immediately, the hip moves into extension reaching about

20 degrees of flexion at mid support, and about 5 degrees of extension at take-off.

Entering into the swing phase, the hip reaches maximum extension of 20 degrees at the end of follow through, and then immediately reverses into hip flexion during forward swing.(Loudon et al., 2013) A maximum hip flexion angle of 65 degrees is achieved towards the end of mid swing, followed immediately by 25 degrees of extension while the foot readies itself to make contact with the ground. A significant, negative correlation between hip extension and anterior pelvic tilt has been exhibited in recreational runners.(Franz, Paylo, Dicharry, Riley, & Kerrigan, 2009) Runners that exhibited reduced peak hip extension had greater anterior pelvic tilt indicating that the body compensates for lack of movement of one joint at another, which can lead to injury.

Frontal plane hip abduction/adduction reflects the motion of the pelvis during running. At initial foot contact the hip is in approximately 7 degrees of hip adduction for males and 11 degrees for females.(Willson, Petrowitz, Butler, & Kernozek, 2012) From foot contact through mid-support the hip abducts slightly reaching a position of hip abduction at take-off. During swing phase a maximum hip abduction angle of 8 degrees is reached; however this returns back to neutral at the time of foot descent before the next foot contact.

Internal and external rotation of the hip is minimal during running.(Loudon et al.,

2013) At initial foot contact the hip is in slight external rotation and moves into hip internal rotation through mid-support phase. From mid-support to take off the hip internally rotates to a point of neutral hip (0 degrees rotation) at take-off.

Knee Kinematics. During running, the knee is flexed at 15 to 25 degrees when initial foot contact occurs with the ground.(Dugan & Bhat, 2005) Increased knee flexion

30 is crucial at foot strike to attenuate the impact forces acting as a shock absorber.(Novacheck, 1998) Next, in the mid-support phase, knee flexion increases to approximately 40 degrees. As the body moves anteriorly over the lower limb, the knee begins to straighten reaching 15 degrees of flexion at take-off, and even may continue to extend further into the follow-through subphase of swing phase. Once forward swing phase beings the knee moves into 90 to 130° of knee flexion to decrease the lever arm of the swing leg thereby increasing energy efficiency.

Frontal plane movement at the knee is minimal due to ligamentous support of the collateral ligaments. At foot strike, males begin in neutral abduction/adduction, whereas females start in approximately 3 degrees of knee abduction.(Willson et al., 2012) For both males and females the knee slightly abducts until mid-support phase, and then adducts to return to neutral at take-off. The total joint excursion of the knee within the frontal plane is not statistically different between males and females. Additionally, there is a relationship between ankle and knee frontal plane movement.(Dugan & Bhat, 2005)

During ankle pronation, the knee is in a valgus position, and when the ankle is in supination the knee assumes a varus alignment.

Ankle and Foot Kinematics. The talocrural or true ankle joint permits motions in the sagittal plane (plantar flexion and dorsiflexion) while the subtalar joint permits frontal plane motion of the foot (inversion and eversion). At foot contact, the position of the talocrural joint is approximately 5 degrees of plantar flexion to neutral, and then immediately moves to about 10 degrees of dorsiflexion as the heel is lowered to the ground.(Loudon et al., 2013) In the mid-support phase the trunk and stance leg is moved anteriorly over the stationary foot placing the ankle joint in approximately 20 degrees of

31 dorsiflexion. As the momentum carries the body forward, the heel is lifted off of the ground moving the ankle into plantar flexion. At take-off the ankle is in approximately 25 degrees of plantar flexion. During swing phase, the ankle moves from plantar flexion to dorsiflexion in the forward swing phase, and then back to plantar flexion at the end of foot descent and right before the next foot contact.

A runner who is a rearfoot striker will make initial foot contact with the ground in

6 to 8° of inversion, striking first with the heel.(Nicola & Jewison, 2012) Immediately after heel strike until mid-support, the foot moves into eversion, unlocking the transverse tarsal joint allowing the foot to attenuate the ground reaction forces. The greatest amount of inversion (6 to 8°) occurs at approximately 40% of the entire stance phase. Then, at mid-support phase the subtalar joint moves into eversion, locking the tarsal joints and providing a rigid lever for take-off.(Dugan & Bhat, 2005)

2.3.3 Foot Strike Patterns

Initial foot contact with the ground during running can occur at three separate regions of the foot, representing the three running foot strike patterns. A runner with a rearfoot strike (RFS) pattern will make initial contact with the ground at the heel,(Lieberman et al., 2010) while a runner with a midfoot strike (MFS) pattern plants the foot on the ground with the heel and ball of the foot landing simultaneously, almost as if running flat footed. Lastly, a runner who strikes with the forefoot (FFS) will land on the ball of the foot before the heels comes down. In an analysis of 1,991 recreational and elite runners during a marathon race, 93.67% ran with a RFS, 5.07% with a MFS, and

0.55% with a FFS pattern.(Kasmer, Liu, Roberts, & Valadao, 2013) Additionally,

32 throughout a long distance race the prevalence of RFS runners has increased from 87.8% to 93.0%, indicating the possible influence of fatigue on the alteration of foot strike patterns.(Larson et al., 2011)

The degree of sagittal plane range of motion at the ankle during impact as well as the location of ground impact is different between runners with a RFS and FFS pattern.(Lieberman et al., 2010) A runner with a RFS pattern when running shod makes impact with the ground just inferior to the ankle, with the ankle in dorsiflexion

(9.3±6.5°). On the other hand, a runner with a FFS pattern when running shod will make impact with the ground under the ball of the foot in ankle plantarflexion (-8.1±15.9°) and continue to move into dorsiflexion as the heel is lowered. Additionally, the plantar foot angle, or the angle between the horizontal ground and the plantar surface of the foot is greater in RFS runners compared to FFS runners.(Lieberman et al., 2010) RFS runners have a greater dorsiflexion angle between the ground and plantar surface of the foot

(28.3±6.2°) compared to FFS runners (2.2±14.0°).

Due to differences at the ankle, additional lower extremity running kinematic alterations are visible between runners with a RFS and FFS pattern.(Daoud et al., 2012)

For example, a RFS runner tends to land with the foot anterior to the knee and hip, with a knee in near terminal extension. On the other hand, a FFS runner impacts the ground with the foot underneath the center of mass and with greater knee flexion. A MFS runner tends to be variable but has kinematics between that of RFS and FFS runners.

Foot strike patterns have been classified using kinematic data from high speed cameras, more specifically classifying by the plantar foot angle between the running surface and plantar surface,(Lieberman et al., 2010) and by point of initial contact of the

33 foot with the ground.(Kasmer et al., 2013) However, these methods require expensive equipment and a time intensive detailed analysis frame by frame of running gait.

Additionally, foot strike patterns have been classified using kinetic data, in particular peak vertical ground reaction forces during the impact in the stance phase of running.(Lieberman et al., 2010) Impact peak has been used as a kinetic indicator between foot strike patterns, however it can be related to numerous other issues such as cadence, footwear, and speed.

A more recently utilized method for classifying foot strike pattern is the time between heel and metatarsal peak accelerations (THM).(Giandolini et al., 2014) A significant correlation between THM and the angle at foot contact was strong for a variety of speeds, slopes and foot strike patterns (r=0.92). Researchers classified RFS runners with a THM greater than 15.2ms, MFS between 15.2 and -5.49ms, and FFS less than -5.49ms.

2.3.4 Muscle Activation Patterns during Running

Running can only be conducted smoothly should the muscles controlling the lower extremity movements be strong enough and timed efficiently. Muscles from the abdomen and back all the way down to the toe flexors and extensors work in unison specific sequence. When chaos occurs and timing is off, injury can occur.

Trunk and Pelvic Muscle Activation. The muscles of the abdomen, back, and hip girdle, along with the gluteal and diaphragm muscles work collectively to control breathing and perform the necessary trunk flexion and rotation motion required during running.(Schache et al., 1999) When the pelvis rotates internally and externally with each

34 stride, the muscles of the trunk keep the spine and abdomen stable. During the stance phase of running, the gluteus medius is responsible for maintaining a neutral and stable pelvis.(Dicharry, 2010) Posterior and anterior pelvic tilt is performed with contraction of the hamstrings and quadriceps respectively.

Hip Muscle Activation. At initial foot contact the hamstring muscles and the gluteus maximus are contracting eccentrically to limit hip flexion and stabilize the stance limb. The gluteus medius and tensor fasciae latae are attempting to limit the degree of hip adduction range of motion by counteracting the hip adductors that are working concentrically. As the limb moves into the mid-support phase, the gluteus medius and tensor fascia latae are acting eccentrically to maintain a level pelvis from which the swing leg moves. All the way through to take-off, the gluteus maximus and hamstrings are concentrically moving the limb into hip extension. Hip extension at take-off is primarily facilitated by the gluteus maximus.(Schache et al., 1999) Also at take-off the gluteus medius is concentrically performing hip abduction. Overall, females have demonstrated greater peak and average gluteus maximus activation during running compared to males.(Willson et al., 2012) No differences in gluteus medius activation between females and males has been established.

During the beginning of swing phase, the hamstrings and gluteus maximus extend the hip to pull the body forward, while the hip flexors eccentrically contract to control excessive hip extension. Subsequently, the hip flexors, iliopsoas, rectus femoris and tensor fascia latae, become the primary force generators for forward swing driving the hip into flexion. Finally, during foot descent the gluteus maximus and hamstring muscles

35 decelerate the thigh as it moves into flexion and the gluteus medius and tensor fascia latae prepare the pelvis for contact.

Knee Muscle Activation. The quadriceps femoris muscle group and the hamstring muscle group are active prior to initial foot strike to prepare the stance limb for ground contact. The hamstring muscles slow the rapidly extending knee, while the quadriceps muscles act as braking forces providing the primary means of shock absorption from initial contact to mid-support.(Novacheck, 1998) From mid-support to take-off the quadriceps muscles then work eccentrically to resist knee flexion. Once the swing phase begins, the hamstrings concentrically move the knee into extension. As forward swing is initiated the quadriceps and hamstrings muscles co-contract, generating minimal power.(Novacheck, 1998) During foot descent the hamstring muscles slow knee extension by contracting eccentrically.

Ankle and Foot Muscle Activation. The anterior tibialis muscle is activated instantly at initial foot contact in order to control the foot slap or downward momentum of the forefoot.(Loudon et al., 2013) However, control of the foot slap is only present in the rearfoot, and slightly in the midfoot striker, while it is absent in a forefoot striker.

Also during initial contact the ankle plantarflexors are eccentrically contracting to help absorb the impact. After initial contact and through mid-support the center of mass falls medial to the stance limb forcing the gastrocnemius and soleus to work eccentrically to stabilize the subtalar joint and limit excessive pronation. From mid-support to take-off the gastrocnemius is the primary generating of the anterior propulsive energy.

Additionally during take-off the toe flexors and fibularis muscles are concentrically

36 contracting to assist in the propulsion of the body, while the toe extensors are working to stabilize the toes for a stable take-off.

During the swing phase the gastrocnemius initially concentrically contracts through follow through. Then during forward swing the ankle dorsiflexes to provide clearance of the foot over the ground. Lastly, during foot descent the tibialis anterior maintains dorsiflexion to prepare the foot for its next contact with the ground.

2.3.5 Ground Reaction Forces during Running

Ground reaction forces (GRFs) are the forces exerted by the ground on the foot during ground contact, such as during the stance phase of running.(Ounpuu, 1994) The magnitude of the vertical GRFs during the stance phase of running varies between 2 and

6 times the runner’s body weight, and is dependent on running speed and foot strike pattern. As running speed increases, so does the peak force amplitude.

Runners with a RFS pattern exhibit a small impact force in the first 20% of the stance phase of running followed by a larger gradual peak for the remainder of stance phase.(Cavanagh & Lafortune, 1980; Ounpuu, 1994) The first impact peak rises to about

2.2 times body weight in approximately 23 milliseconds. The second impact peak is reached slowly (83 ms) with a maximum impact peak of about 2.8 times body weight.

On the other hand, a MFS runner shows a small but recognizable first impact peak on a continuum towards a larger gradual second impact.(Cavanagh & Lafortune, 1980) The peak vertical GRF is approximately 2.7 times body weight in magnitude and is reached approximately 75ms after initial contact. Lastly, runners with a FFS pattern generate an impact, however lack a clear impact peak as the stance phase is more compliant and

37 involves the exchange of less momentum due to increased ROM at the ankle and knee.(Lieberman et al., 2010)

2.3.6 Center of Pressuring during Running

The point of contact through which the GRFs are exerted on the foot is termed the center of pressure (COP). The position of the COP on the foot will vary between runners with different foot strike patterns. A runner with a RFS pattern makes contact with the heel on the posterior lateral third of the shoe, while a MFS runner lands on the central, lateral third of the shoe. The path of the COP is the same for RFS and MFS runners, as it follows along the lateral border to the center of the forefoot, and continues over the great toe as the runner moves into take-off. The COP for a FFS begins around the base of the

4th and 5th metatarsals, then moves medially and off the big toe during take-off.

2.4 Running Related Injuries

2.4.1 Epidemiology or RRIs

Running continues to provide substantial physical and psychological health benefits to the millions of Americans that chose to run as their primary form of physical activity. However, despite all of the health benefits, running related injuries (RRIs) are rampant, particularly of the lower extremity and back. Researchers have utilized prospective studies to track the incidence rate of new RRIs sustained by runners over a given period of time and has been recorded between 16 and 85%.(van Gent et al., 2007)

Whereas, other researchers have utilized surveys and questionnaires to determine the retrospective prevalence rate of runners who report a history of a RRI at a given point in 38 time; this rate is between 8 and 55%.(van Middelkoop et al., 2008; van Poppel, Scholten-

Peeters, van Middelkoop, & Verhagen, 2013) Rates of RRIs vary significantly as the study design, definition of injury and population of runners varies between research studies.

2.4.2 Definition of a RRI

The use of definitions to describe running related injuries (RRI) dates back to

1987 when Lysholm and Wiklander conducted a prospective study tracking RRIs in elite runners.(Lysholm & Wiklander, 1987) The definition of a RRI utilized in the study was any injury that hindered training or competition for at least one week. More recently researchers have coined the term running related musculoskeletal injuries (RRMI) to specify injuries of the musculoskeletal system, separating out illnesses and basic first aid injuries as a result of running.(Lopes, Hespanhol Junior, Yeung, & Costa, 2012) Several

RRI definitions include the impact of the injury on running specifically. For example,

Bovens et al defined a RRI as “any physical complaint developed in relation with running activities causing a restriction in running distance, speed, duration, or frequency”.(Bovens et al., 1989) Other investigators have solely included the injuries impact on weekly running distance,(Macera et al., 1989; Walter, Hart, Mcintosh, &

Sutton, 1989) running pace,(Wen, Puffer, & Schmalzried, 1998) or distance and speed combined.(Taunton et al., 2003) Differences in the definition in regards to the impact on running/training can impact the incidence rate, as the rate of injury from the aforementioned studies range between 26-51.5%.

Additionally, variations exist between definitions in the time frame in which the injury restricted or removed the individual from running. For example, the definition utilized by Buist et al was “any self-reported running-related musculoskeletal complaint of the lower extremity or back causing restriction of running for at least one week, or three consecutive training sessions”.(Buist, Bredeweg, Lemmink, van Mechelen, &

Diercks, 2010) Other researchers indicate no time frame in the definitions, thus RRIs may have impacted running for less than three days, or significantly more than 3 days.(Lun, Meeuwisse, Stergiou, & Stefanyshyn, 2004; Wen et al., 1998) Few authors have addressed this issue by grading injuries according to modification or stoppage of running/training, often terming it severity of injury classification.(Lun et al., 2004; Marti,

Vader, Minder, & Abelin, 1988; Parker et al., 2011) A six point classification has been utilized more often, however with different definitions. A “1” according to Lun et al is a

“reduction in running mileage for 1 day” compared to Parker et al that classifies a “1” as

“no change in running pace or routine”. (Lun et al., 2004; Parker et al., 2011) Both scales progress to a “6”, however again the earlier would be “stoppage of running for more than

7 days”, while the later has a “6” representing “stopped running for more than one month”.(Lun et al., 2004; Parker et al., 2011) Once again, differences in severity rating can impact the interpretation and comparability between RRI rates. Perhaps a simple solution would be reporting days missed and/or modified activity rather than creating a classification system.

Another variation between definitions is whether the runner sought medical attention from a health care professional for the injury.(Macera et al., 1989; Taunton et al., 2003; Walter et al., 1989) Some studies provided a health care professional to which

40 participants could go to and report an injury,(Taunton et al., 2003) whereas other studies indicated injuries only if the participants went to a health care professional and reported the injury.(Macera et al., 1989; Walter et al., 1989) Others definitions did not indicate whether a health care professional was involved, thereby the injury diagnoses may not be correctly reported by the participants. Additionally, comparison between studies utilizing different RRI definitions should be interpreted carefully, as some definitions include injuries to the entire body,(Bovens et al., 1989; Lysholm & Wiklander, 1987; Taunton et al., 2003) whereas others only include injuries to the lower extremity and back.(Bredeweg, Buist, & Kluitenberg, 2013; Buist, Bredeweg, Lemmink, et al., 2010)

Lastly, several definitions within the literature do not specify if new and/or recurring

RRIs are used in the analysis. Walter et al indicated in his results that 26% of runners sustained a new RRI over a 12 month observation period.(Walter et al., 1989) On the other hand, Lun et al classified injuries as new or recurring, and found 79% of runners sustained a RRI over the course of 6 months.(Lun et al., 2004) It is important for researchers to differentiate between new and recurring injuries within the data analysis as recurring injuries can inflate the true incidence rate of new RRI. However, it is still important to track recurring injuries to understand why some runners continually sustain

RRIs while training.

2.4.3 Rates of RRIs

Researchers have examined the incidence of RRIs in a variety of running populations, of which can be further characterized by gender and age, running event/distance, group training program involvement, and timing of the injury.

Additionally, researchers have investigated characteristics of RRIs including whether professional medical advice was sought, and the impact of the injury on running and physical activity. It is important to not only understand the incidence or prevalence of

RRIs, but also how runners manage the RRI.

RRI Rates by Gender and Age. Male and female runners appear to exhibit injuries at similar rates. The incidence of RRIs in males is between 14.3-58.6%, and between

17.3-51.1% for females.(Bredeweg et al., 2013; Buist, Bredeweg, et al., 2010a; Macera et al., 1989; Walter et al., 1989) One of the largest prospective studies examining RRI rates examined 1,680 runners over 12 months of training leading up to a variety of races (2.5 to

14 miles), of which 1,288 runners completed the follow up.(Walter et al., 1989)

Approximately 49% of males and 45.5% of females sustained an injury over the 12 month follow up period. This is relatively consistent with RRI rates reported by Macera et al at 52% for males and 49% for females over a 12 month follow-up period.(Macera et al., 1989) It is important to note that individual diagnoses and locations of RRIs will differ between genders, which will be addressed shortly.

Limited studies have examined the difference in injury rates between runners of various ages. Masters runners, or runners over the age of 40 years, reported more injuries than younger runners aged 39 years or less.(McKean, Manson, & Stanish, 2006) A total of 446 of 949 (49%) masters’ runners reported an injury over 12 months that affected their ability to train or race compared to 843 of 1,876 (45%) younger runners. Differences in injury rates within this study could be attributed to the masters runners running significantly more times per week compared to younger runners, as well as compared to healthy masters’ runners. It could be possible that musculoskeletal repair from regular

42 running may take more time in older athletes, just as it takes more time for the body to heal from an injury.(Karamanidis & Arampatzis, 2005) Future research should examine recovery time from musculoskeletal damage both caused by running and RRI.

RRI Rates by Running Event or Distance. Runners training for a marathon are thought to sustain a higher rate of RRIs due to overload and fatigue of the supporting tissues of the lower extremity during the long training sessions necessary to prepare oneself for the 26.2 mile race.(Harrast & Colonno, 2010; Maughan & Miller, 1983)

Chang et al conducted a retrospective survey asking participants who competed in a full marathon, half marathon, and 10km race if they had a previous history of a RRI.(Chang,

Shih, & Chen, 2012) Forty eight percent of marathoners, 42.4% of half marathoners, and

44.6% of 10km race runners reported a previous RRI of the lower extremity. Although the prevalence rate of injuries did not significantly differ between runners training for different events, those who competed in the 10km race reported significantly more hip pain during running, whereas the marathon runners reported more ankle/foot pain.(Chang et al., 2012) Pain located in the ankle/foot for marathoners could be attributed to the repetitive pounding on hard surfaces.

Additional investigation into the RRI amongst marathoners identified 58% have incurred an injury in preparation for a marathon race.(Maughan & Miller, 1983) Of the runners reporting an injury, 73% considered the RRI serious enough to interrupt their normal training program. The incidence of drop-out while training for a marathon due to an injury is approximately 36%.(Clough, Shepherd, & Maughan, 1989) Forty nine percent of the runners that dropped out while training for a marathon reported sustaining an injury while training, compared to 41% of runners who finished the marathon. Injuries

43 reported by runners who dropped out required more healing time (1 to 8+ weeks, 89%) than injuries reported by marathon finishers (65%). On the contrary, 29.5-48.4% of runners training for races between 2.5 and 14 miles in distance sustained injuries while training for the race of their choice.(Taunton et al., 2003; Walter et al., 1989) However, these studies used different definitions of injury, did not always differentiate between new and recurring injuries, did not all distinguish if the injury occurred as a result of running, and did not all require a diagnosis by a medical professional. Therefore, the comparison of injury rates between studies should be considered carefully.

Lysholm and Wiklander examined the incidence rate of RRIs in elite runners training for various running events including sprinters, middle-distance runners, and long-distance runners.(Lysholm & Wiklander, 1987) Long-distance runners had the lowest incidence rate at 57% over one year, followed by sprinters (68%) and middle- distance runners (77%). The sample size could be a limitation as the study only had 60 participants. Additionally, the incidence rate seems relatively low considering the injury definition required that the injury hinder training or competition for at least one week.

Hence the researchers could have missed injuries that had symptoms lasting for less than one week.

Rates for Group Training Programs. Group training programs (GTP) have increased in popularity and help runners prepare for and/or improve their performance.

GTPs are designed to provide a structured, well planned progression to a designated event while simultaneously minimizing training related errors which have been identified as a significant risk factor for injury.(van Gent et al., 2007) Despite the goal of GTPs to reduce injury, Parker et al identified that there was no difference in the prevalence of

RRIs between participants in a marathon GTP and those not in a GTP.(Parker et al.,

2011) Approximately 39% of participants in a marathon GTP sustained an injury during training compared to 34% that were not involved in a GTP but training for the marathon.

Additionally, about 17% of participants in the GTP sustained an injury during the marathon, compared to 11% of runners who trained on their own for the marathon. A higher rate of RRI within the GTP group could be due to “standardized” GTP plans vs. individualized plans. Additionally, although not recorded, participants with minimal running experience may have felt “peer pressure” to run beyond their individual abilities, and possibly sooner than their body was prepared for. Future research should identify whether participants in a GTP consistently stuck with the program. Perhaps runners that modified the program or ran fewer days than the plan recommended were more likely to sustain an injury. On the other hand, perhaps runners that did more than the program entailed were more likely to endure a RRI.

Professional Medical Attention. Research studies investigating the rate of RRIs reported by runners have identified that 33-70% of injured runners will seek out medical attention for an injury. (Jacobs & Berson, 1986; Lun et al., 2004; Maughan & Miller,

1983) Marti et al found that runners who ran more than 50 km per week were six times more likely to seek medical attention compared to runners who ran 1-10km per week.(Marti et al., 1988) One could speculate that runners who run fewer miles per week may be able to take more time to rest and allow injuries to heal, whereas runners who run more mileage per week may be more committed, and do not wish to be removed from running, thus they seek medical treatment to find a way to keep them active. Of the runners who sought medical attention, 36% felt they followed their physicians advice

45 completely, 45% reported almost, and 20% reported somewhat.(Jacobs & Berson, 1986)

Medical advice may not be followed often as the most commonly recommended treatment by physicians is rest. Runners report lack of compliance to medical advice as the injury healed on its own, the runner did not want to reduce speed or distance, the recommended treatment was too time consuming, and lack of trust of the physicians advice. Additionally, highly committed, high mileage runners report feelings of agony and depression when runs are missed, hence they may not listen to medical advice to rest following an injury.(Carmack & Martens, 1979)

When comparing novice and regular runners enrolled in a GTP, 48% of novice runners and 24% of regular runners did not return to running after sustaining a

RRI.(Buist, Bredeweg, et al., 2010b) Novice runners may be at a greater disadvantage after sustaining a RRI as they may not have the time remaining prior to the event to train for and do well in a race, whereas a regular runner may have the mileage and experience to bounce back into running quicker and smoother. Additionally, regular runners may have a better awareness of their body’s abilities and be able to gauge whether or not they are capable of performing a run, compared to a novice runner who may opt out of running altogether.

2.4.4 Specific Diagnoses/Types of RRIs

Similar to the variability in the incidence rates of injuries, current research literature provides no clear consensus as to the most prevalent location of injury and specific RRI diagnoses amongst runners. Differences in location and diagnosis of injury vary by gender, age and training distance. Across all runners, the three most prevalent

46 locations of RRMIs are the knee (12.7-33.3%), lower leg (12.0-30.9%), and ankle (5.5-

23.5%).(Taunton et al., 2002b) The five most commonly reported RRMI diagnoses are medial tibial stress syndrome (MTSS), iliotibial band syndrome (ITBS), Achilles tendinopathy, patellofemoral pain (PFP),and plantar fasciitis.(Jakobsen, Kroner, Schmidt,

& Kjeldsen, 1994; Lysholm & Wiklander, 1987; Macintyre et al., 1991; McKean et al.,

2006; Taunton et al., 2002a)

Gender Differences in RRIs. Reports on RRI rates by location and diagnoses suggest little differences amongst males and females.(Lun et al., 2004; Taunton et al.,

2003; van Poppel et al., 2013) For both males and females the most common location for an RRI is the knee at 13-36% and 22-35% respectively. Males report higher rates of lower leg (13-17%)(Lun et al., 2004; Taunton et al., 2003), and Achilles injuries

(16.5%),(van Poppel et al., 2013) whereas females report more hip (13.8%),(van Poppel et al., 2013) and thigh (9%) (Lun et al., 2004) injuries. For males, the top five RRI diagnoses are PFP (13.4%), plantar fasciitis (9.2%), meniscal injuries (7.5%), ITBFS

(6.8%), and Achilles tendinitis (6.0%).(Taunton et al., 2002a) The top five RRI diagnoses for females are PFP (19.2%), ITBS (9.8%), plantar fasciitis (6.8%), tibial stress syndrome (5.2%), and gluteus medius injuries (4.9%).(Taunton et al., 2002a)

Age Differences in RRIs. Few studies have examined different RRIs in runners by age groups, all of which have been conducted retrospectively.(Hogan & Cape, 1984;

McKean et al., 2006) Older runners have been classified as over the age of 40(McKean et al., 2006) or 60 years.(Hogan & Cape, 1984) Injuries have been theorized to be more prevalent amongst older runners as numerous physiological adaptations occur with age, including a decrease in strength, flexibility, bone density and proprioception.(McKean et

47 al., 2006) The most common location of RRIs in runners 40 years or older is the knee

(19.6%), followed by the foot (16.2%) and the hamstring (11.7%).(McKean et al., 2006)

This is similar to runners 39 years or younger who sustain most RRIs at the knee (24.8%) and foot (16.2%), followed by the lower leg (11.3%).

The most common diagnoses for older runners are different compared to younger runners.(McKean et al., 2006) The three most common RRI diagnoses in older runners are plantar fasciitis (9.8%) quadriceps/hamstring tendinitis (8.1%), and Achilles injuries

(6.2%). On the other hand, the three most common RRI diagnoses for younger runners are iliotibial band injuries (7.7%), plantar fasciitis (7.6%), and shin injuries (7.1%).

Achilles, quadriceps, and hamstring injuries could be more prevalent within older runners as muscle tendon unit function has been shown to be reduced with age resulting in decreased muscle strength and musculoskeletal stiffness.(Karamanidis & Arampatzis,

2005) However, future research should investigate the direct relationship between RRI and strength across runners of all ages.

Training Distance Differences. Only one study to date has examined the differences in RRI location between runners competing in different events.(Lysholm &

Wiklander, 1987) The researchers reported that more middle distance runners sustained injuries (77%) compared to sprinters (68%) and long distance/marathon runners (57%).

This could be attributed to more variety in the training workouts, including fartlek’s, speed workouts, tempos, and distance runs. Long distance runners sustained significantly more injuries of the foot (33.3%) compared to sprinters and middle distance runners

(2.7%; P<0.002). Injuries to the foot are common amongst marathoners probably due to the repetitive foot contact for longer distances compared to non-marathon runners.

Additionally, middle and long distance runners sustained more back and hip injuries

(20.6%) compared to sprinters (0%; p<0.05). Lastly, sprinters sustained significantly more hamstring injuries (42.9%) compared to middle and long distance runners combined

(2.9%, p<0.001). Hamstring injuries are more prevalent amongst sprinters during the follow-through of swing phase, which is accentuated in sprinters, as it is also when peak musculotendinous force and load within the hamstring muscles occurs.(Schache, Dorn,

Blanch, Brown, & Pandy, 2012)

A retrospective study conducted by Macintyre et al examined 1,819 injuries in 1,

650 runners.(Macintyre et al., 1991) Runners were classified as middle distance, marathon, and recreational runners, and further grouped by gender. Middle distance runners were elite runners training for races at the distances of 800 to 5,000 meters.

Marathon runners were the runners completing high mileage and who ran at least one marathon per year. Lastly, recreational runners were the runners who choose running as their primary sport and participated in much lower weekly mileage. The most common site of injury for runners of all degrees and both genders, except female middle distance runners was the knee (27-51.5%). For males, the highest rate of injuries to the knee was seen amongst recreational runners (49.0%), whereas the highest rate was seen in female marathon runners (51.5%). The most common site of injury for female middle distance runners was the lower leg (35.1%). The second most common location for injury amongst marathoners differed between males and females, with males having lower leg injuries (21.9%) and females more foot injuries (15.5%). The second most common injury amongst recreational runners was similar for both males and females at the lower leg (19.1-21.5%).

Amongst all runners, middle distance, marathoners, and recreational runners, PFP was the most common diagnosis (17.5-30.2%).(McKean et al., 2006) When analyzing injuries by diagnosis, the three most common RRIs in both marathon and recreational males were PFP (17.5-, 5.3%), ITBS (11.8%, 6.7%), and plantar fasciitis (5.7%, 5.2%).

For middle distance males the three most common injuries were PFP (21.4%), tibial stress fracture (10.7%), and MTSS (7.2%). Women marathoners and recreational runners exhibited the same trend; the most common injury was PFP (23.2%, 30.2%), followed by

ITBS (21.2%, 7.2%), and plantar fasciitis (6.1%, 7.2%). Female middle distance runners on the other hand displayed a different tendency of injury with the most common RRI being PFP (18.9%), trailed closely by tibial stress syndrome (16.2%), and then Achilles tendinitis (10.8%). The prevalence of tibial injuries amongst middle distance runners could be attributed to the fact that they are elite runners training harder and potentially with more speed and interval workouts. In addition to training patterns, additional differences amongst injury rates could be attributed to numerous including shoe type and wear, musculoskeletal characteristics, and previous injury history.

2.4.5 Risk Factors for RRMIs

Prospective studies measure variables within a group of individuals prior to an injury occurring. Once injuries occur, the injured individuals are compared to individuals who did not sustain an injury. From this data, a prospective study can determine risk factors. On the other hand, a retrospective case control study compares a group of individuals with a given injury to a healthy control group. From a retrospective case control study association factors, or factors associated with the injury, can be established.

Risk factors provide valuable insight into what places an individual at an increased risk for a given injury of interest. Thus if risk factors are established, preventive measures can be taken to reduce ones risk of injury. Risk factors for all RRMIs can be categorized as demographic (age, height, weight, gender.), health (previous injury), and training related

(running experience, miles ran per week, days ran per week, etc.).

Demographic Risk Factors. Age has been reported to be both a risk factor(Macera et al., 1989; Taunton et al., 2003; Wen et al., 1998) and protective factor for

RRIs.(Taunton et al., 2003) In a prospective study of 255 runners participating in a GTP in preparation for a marathon, 90 runners sustained an overuse injury.(Wen et al., 1998)

A high age placed runners at about two times greater risk for knee overuse injuries

(RR=2.091, 95%CI: 0.954-4.583). Additionally, males with a high age while performing regular training were at a minimal increased risk for sustaining a lower extremity RRI

(OR=1.0, 95%CI:1.0-1.0).(Macera et al., 1989) However, for both studies an age cut-off was not reported, making it difficult to interpret the meaning of a “high age”. Amongst

844 recreational runners participating in a GTP to prepare for a 10km race, 249 injuries were reported over 13 weeks.(Taunton et al., 2003) Females over the age of 50 years had two times greater risk of sustaining a new or recurring injury (RR=1.919, 95%CI: 1.107-

3.328). However, females less than 31 years of age sustained fewer new injuries compared to female runners 31 years or older (RR=0.575, 95%CI: 0.342-0.967). As noted previously, it has been speculated that injuries are more common amongst older runners as physiological adaptations occur with age.(McKean et al., 2006) However, additional research is necessary to support these hypotheses in runners.

Male runners considered to be of average height (170-180cm) and tall height

(>180cm) were reported to be at two times greater risk for sustaining a new injury compared to short male runners (<170cm).(Walter et al., 1989) This trend was not as clear between females, possibly due to the unequal distribution of females within the chosen height categories. This is the only study to report height as a risk factor, hence additional research is necessary to support or refute these findings.

Only two studies have investigated the risk of body mass index (BMI) on RRIs and have found confounding results.(Macera et al., 1989; Taunton et al., 2003) Being overweight can increase joint loading beyond the ability of the musculoskeletal structures, possibly leading to injury and in the future osteoarthritis.(Hunter & Eckstein,

2009) The World Health Organization (WHO) reports that people with a BMI less than

25 kg/m2 are healthy, 25-30 kg/m2 are overweight, and greater than 30 kg/m2 are obese.(WHO, 2009) Taunton et al reported that male runners with a BMI greater than 26 kg/m2 are at a decreased risk for sustaining an injury while training (RR=0.407,

95%CI:0.211-0.785).(Taunton et al., 2003) In contrast, Macera et al found that BMI was not a risk factor for sustaining a RRI when included in a regression analysis.(Macera et al., 1989) Due to conflicting results, additional research should be conducted analyzing the risk of BMI and weight as research consistently shows higher body mass can lead to an increase in the breakdown of the musculoskeletal system.(Hunter & Eckstein, 2009)

Although injury rates between males and females have been reported to be similar, females may be an increased risk of an RRI compared to males depending on the volume of training and location of the injury. Macera et al found that females training for a marathon were at 1.5x greater risk of sustaining a lower extremity musculoskeletal

52 injury compared to males, while females training for a 10km race are not at an increased risk compared their male counterparts.(Macera, Pate, Woods, Davis, & Jackson, 1991)

Research has determined that overall RRI rates are similar between males and females, however that RRIs vary by location and diagnoses. Therefore, future research should examine the risk of RRI for males and females based on specific locations of injury as it is important to determine what risk factors predispose females to specific RRIs compared to males.

Health Risk Factors. A history of a previous injury consistently has been reported to be a risk factor for sustaining an additional RRI.(Buist, Bredeweg, Lemmink, et al.,

2010; Macera et al., 1989; Macera et al., 1991; Walter et al., 1989; Wen et al., 1998) For example, it has been suggested that injury RRI in the previous 12 months may not have healed completely making the runner more susceptible to an additional RRI.(Macera,

1992) Also, it has been theorized that runners with a previous injury may have biomechanical alterations that continually go unaddressed, leading to repetitive injuries.

Males who have a previous history of an injury in the 12 months prior to participating in a group training for a 4 mile and 26.2 mile event are at 2.02 to 2.64 times greater risk for sustaining an injury compared to male runners with no previous history of an injury.(Buist, Bredeweg, Lemmink, et al., 2010; Wen et al., 1998) Similarly, females who have sustained an injury in the previous year prior to training are 2.35 times more likely to sustain an additional new or recurring injury compared to a female runner with no previous injury history.(Walter et al., 1989) Distance ran per week has been thought to increase a runners risk of injury.(Macera et al., 1989) When accounting for distance ran, males and females with a history of a new lower extremity injury in the previous 12

53 months were still at a two times greater risk of sustaining another lower extremity injury compared to male and female runners with no injury history. Therefore, runners who ran fewer miles per week were at an equal risk of sustaining another lower extremity injury as runners who ran a greater amount of miles per week.

When narrowing in on lower extremity RRMI only, males and females were at a

6.3 and 7.6 times greater risk respectively for sustaining a new lower extremity RRMI if they had a previous musculoskeletal problem in the past 12 months compared to runners who did not have a history of musculoskeletal problem.(Macera et al., 1991) As stated previously, the definition of injury will effect injury rates, and also risk of injury. The risk of injury when utilizing a definition that consists of only RRMIs increases future risk, compared to a definition including all injuries of the body and /or non-running-related injuries. Only one study has investigated the risk of a specific injury history, shin injuries, on the development of the same injury during training.(Wen et al., 1998) Males and females that had a history of a shin injury within 12 months leading up to the training program, were seven times more likely to sustain another shin injury while training for a marathon (RR=7.235, 95%CI:2.339-21.815). Additional research investigating the risk of previous injuries on the development of the same injuries would be beneficial.

Only one study has investigated the risk of RRI during training and during a marathon race, based on the severity of a previous injury. (Parker et al., 2011) Three hundred and seventy eight female runners trained for a marathon, either on their own or with a GTP. Questionnaires were completed by all participants, in which previous injury history in the past 12 months was reported. Once training started injuries were reported, as well as during the marathon. The authors used a six point scale (1 to 6) to rate injury

54 severity of the previous injuries, and injuries sustained during training and the marathon.

A 1 to 3 represented a mild injury, including injuries that did not change running pace or routine (1), to injuries that slowed pace during running and decreased weekly mileage

(3). Injuries scored a 4 to 6 were considered severe injuries, including injuries that stopped running for less than one week (4) to stopped running for more than 1 month (6).

The authors found that female runners, who reported a mild injury in the 12 months prior to training, were 3.54 times more likely to sustain an injury of any severity during training compared to runners without a previous injury history. On the other hand, female runners who reported a severe injury in the previous 12 months were 5.08 times more likely to sustain an injury of any severity during training compared to runners without a previous injury. Then, those runners with a severe injury in the previous 12 months were

6.43 times more likely to have another severe injury during training. Lastly, runners that had a mild or severe injury in the previous 12 months prior to training were at a 3.79 and

7.09 times greater risk, respectively, for sustaining an injury during the marathon compared to runners without a previous injury history. Severity of injury is significantly associated with the risk of sustaining an injury in the future, as female runners with a previous history of a severe injury, or those who stopped running due to an injury, were at a greater risk for sustaining another injury compared to runners who only had a history of a mild injury, or an injury that only slowed down running. This finding could be due to the fact that severe injuries sustained in the year prior to training did not heal, thus runners were reinjured.(Parker et al., 2011) Additionally, runners with severe injuries may not have corrected any biomechanical abnormalities that caused the first severe injury, thus running with faulty mechanics lead to subsequent injuries. Future research

55 should differentiate between recurring and new injuries. It should be noted that because this research was focused on female runners, these associations cannot be assumed in males, warranting similar research with male runners.

Training Related Risk Factors. To date, running and training related factors are the most investigated risk factors for RRIs. Unfortunately, data for a majority of running and training related factors remain debatable. The association between running experience and lower extremity injury is inconsistent.(Macera et al., 1989; Walter et al.,

1989) It has been reported that males with two or less years, and 10 years or greater of running experience are at 2.2 and 1.2 times greater risk respectively, for sustaining a lower extremity injury during training.(Macera et al., 1989) Similarly, females are at a

1.4 and 1.7 times greater risk for sustaining a lower extremity injury during training if they have two or less, and ten or greater years of experience running, respectively. Males with less than two years of running experience may be more apt to ramp up mileage in a shorter amount of time compared to females, predisposing them to an increased rate of sustaining an RRI. On the other hand, Walter et al reported that running experience was not a risk factor for males and females, as was racing experience.(Walter et al., 1989)

But, the authors did report that competitive runners were at a greater risk for sustaining an injury compared to fitness runners. However, the authors did not define a competitive and fitness runner, therefore no conclusions can be drawn based on what type of competitive runner is at greater risk. When examining injuries by location, males and females with greater running experience were more likely to sustain foot injuries while training for a marathon (RR=1.088, 95%CI:1.027-1.152).(Wen et al., 1998) This finding was not supported for overall injuries, knee injuries, and shin injuries. Foot injuries may

56 be more common amongst marathon runners due to increased time on foot, which is further increased by years of running.

Frequency of runs per week is another debatable factor in its link with risk of injury. It has been suggested that runners who run more days per week do not allow for time between running bouts, thus not allowing the body to recover fully between runs, facilitating a chronic breakdown in musculoskeletal structures that may lead to injury.(Macera, 1992) Males who ran three to seven days per week increased their risk for a new injury compared to running 1-2 days per week.(Walter et al., 1989)

Additionally, this risk increased from 2.49 to 5.92 as the number of days ran increased from 4 to 7 days. Likewise, female runners that ran 4 days per week were 1.91 times greater risk of a new injury, whereas female runners that ran 7 days per week were at 5.5 times greater risk compared to runners that ran 1-2 days per week. On the other hand, female runners participating in GTP and running less than the recommended training days (<3 days per week) were over 3.5 times greater risk for sustaining a RRI compared to female runners who ran three or more days per week.(Taunton et al., 2003) GTPs offer a gradual increase in mileage to build an adequate running foundation. Runners who did not keep up with the training sessions may have made too big of a leap in mileage between training sessions leading to injury. To combat the debate on running frequency, a study was conducted to compare runners with similar running distances per week, that ran 2 to 4 weekly training sessions.(Marti et al., 1988) The authors found no difference in the prevalence of RRIs between runners average 22 km per week, and running two, three, or four training sessions. Hence, cumulative distance may be more indicative of injury than the lack of rest between runs.

Most studies have shown an increased risk for injury with an increase in weekly distance ran.(Macera et al., 1989; Walter et al., 1989) Males that ran 20-29 miles per week were almost two times more likely to sustain a lower extremity injury.

Additionally, this risk amplified as weekly mileage increased, so that male runners running 40 or more miles per week were at almost three times greater risk of injury. This association was stronger in female runners with the risk increasing from 4.2 to 7.4 times as weekly mileage increased from 20-29 to 30-39 miles per week. It is hypothesized that an increase in running mileage exacerbates biomechanical imbalances that are already present creating repetitive micro trauma to musculoskeletal structures and leading to overuse injuries.(Marti et al., 1988)

Other less researched training factors include variation in training days, warm-ups and stretching, and participation in other physical activity and GTPs. Runners that incorporate intense training days, interval training, and hill training are not at an increased when analyzing all RRIs together.(Walter et al., 1989) However, when analyzing solely shin injuries, male and female runners that include interval workouts are at 15 times greater risk of sustaining a shin injury compared to runners that do not utilize interval workouts in their training program.(Wen et al., 1998) Due to the contradicting results when using overall RRIs and shin injuries, additional research on interval training is warranted. Although warming-up and stretching are continually recommended, there is no significant risk for runners that do not warm-up or stretch, compared to runners who did.(Macera et al., 1989; Walter et al., 1989) The available research did not emphasize whether the stretching was performed before or after running, and did not include duration and type of stretching. More research is needed on warming up and stretching

58 and its association to RRI prior to drawing a conclusion. Male runners that participated in non-axial loading physical activity such as swimming and cycling, prior to a GTP were twice as likely to sustain a RRI compared to runners that participated in axial loading physical activities including running and jumping.(Buist, Bredeweg, Lemmink, et al.,

2010) The runners that participated in axial loading physical activity may have been accustomed to repetitive ground contact compared to the runners that participated in non- axial loading physical activities and therefore less prone to injury. Lastly, female participants of a GTP were almost at a 2.5 times higher risk for sustaining an injury during a marathon compared to runners who did not participate in a GTP.(Parker et al.,

2011) GTPs may push runners beyond their capabilities, or runners way not have kept up with their training plan prior to participating in the marathon. Future investigation into

GTPs and their effectiveness at reducing risk of RRIs.

2.4.6 Variables Associated with Specific RRMIs

Demographic, health, and training related risk factors have been analyzed repeatedly when collapsing all RRIs together. More recently, specific RRMIs have been investigated individually in runners, most frequently targeting musculoskeletal abnormalities and weaknesses. Running produces cyclical repetitive forces on the body over the course of months, weeks, or a single running session. When an altered running gait is present, in addition to weakened or faulty anatomy, musculoskeletal structures can endure increased loading, over time leading to overuse RRMIs.(Hreljac, Marshall, &

Hume, 2000) Injuries including MTSS, tibial stress fractures, PFP, and ITBS account for almost half of all RRMIs, and although they have been investigated separately they share

59 similar association factors. To date, few prospective studies have been conducted identifying musculoskeletal risk factors in runners.

Medial Tibial Stress Syndrome. Medial tibial stress syndrome (MTSS) is a RRMI characterized by pain along the distal two-thirds of the posteromedial tibia,(Loudon &

Reiman, 2012) contributed to by bony overloading such as that which occurs during running.(Moen, Tol, Weir, Steunebrink, & De Winter, 2009) Often time MTSS is referred to as medial shin pain or shin splints, and should be differentiate from other lower leg injuries including stress fractures and exertional compartment syndrome.

Similar to other RRMIs, MTSS has risk factors including training errors, shoe wear, running surface, and previous injury history.(Bennett et al., 2001; Plisky, Rauh,

Heiderscheit, Underwood, & Tank, 2007) On the other hand, running experience has been found to be a protective factor, with healthy runners having on average 3 more years of running experience compared to runners with MTSS.(Hubbard, Carpenter, & Cordova,

2009)

More recently, musculoskeletal and biomechanical factors for MTSS have been target by researchers. For example, researchers have utilized the navicular drop test as a strong, reliable clinical tool for measuring the degree of pronation at the subtalar joint.(Plisky et al., 2007) Increased pronation has been theorized to place increased stress on the muscles of the deep posterior calf, or occur as a result of muscle dysfunction of these muscles.(Yagi, Muneta, & Sekiya, 2013) In 2001, Bennett et al reported that high school cross country runners that developed MTSS had an increased navicular drop of

6.8mm compared to runners who remained healthy at 3.6mm.(Bennett et al., 2001) In addition, the navicular drop test correctly identified 68% of MTSS cases in the high

60 school cross country runners. However, a more recent investigation utilized the a cut of score on the navicular drop test and established that runners with a navicular drop of over

10mm, are only at a slightly greater risk for developing MTSS compared to runners with a navicular drop of less than 10mm (OR=0.9, 95%CI:0.3-2.8).(Plisky et al., 2007) The utilization of the cut-off as well a difference in measuring technique could have caused differences between the studies.

Passive and active range of motion (Youri Thijs, Els Pattyn, Damien Van

Tiggelen, Lies Rombaut, & Erik Witvrouw) at the ankle and hip have been analyzed in runners using prospective studies.(Bennett et al., 2001; Hubbard et al., 2009; Yagi et al.,

2013) Passive hip internal rotation ROM and active ankle plantarflexion ROM are significantly greater in runners who develop MTSS compared to runners who remain injury free.(Hubbard et al., 2009; Yagi et al., 2013) The difference between groups were

5.6° for hip internal rotation ROM, and 5.4° for active ankle plantarflexion ROM.

Increased passive hip internal rotation ROM has been speculated to lead to altered movement patterns during running, leading to an increase in impact loads distally.(Ferber, Hreljac, & Kendall, 2009) No differences in active ankle dorsiflexion, inversion and eversion ROM, and passive hip external rotation ROM were identified prospectively between healthy runners and runners with MTSS.(Bennett et al., 2001;

Hubbard et al., 2009; Yagi et al., 2013)

Strength of the lower extremity muscles, specifically of the muscles acting upon the ankle joint have been investigated prospectively to determine if differences exist between runners who sustain MTSS and who remain injury free.(Hubbard et al., 2009)

There were no differences in isometric ankle plantarflexion, dorsiflexion, inversion, and

61 eversion strength between collegiate runners who developed MTSS and those that remained injury-free. In a case control study of regularly training athletes, authors found that the athletes with MTSS had greater concentric eversion strength at both 30°/sec and

120°/sec compared to the control group of athletes.(Yuksel et al., 2011) Additionally, the authors noted that the athletes with MTSS also had a greater imbalance of evertor to invertor strength. The authors theorized that having greater eversion strength could lead to excessive pronation during ground contact of running. During the propulsive phase a balanced contraction of the evertor and invertor muscles in crucial. If the ankle evertors are stronger, it could lead to prolonged pronation, placing an additional stress on the posteromedial tibia, which in turn could lead to the development of MTSS.

Faulty running mechanics can be very detrimental, and have been exhibited in runners with medial shin pain compared to injury-free runners.(Loudon & Reiman, 2012)

Runners with medial shin pain show significantly greater pelvic tilt (8.56±2.2°) and peak hip internal rotation ROM (11.48±5.2°), and less knee flexion (37.11±5.4°) compared to injury-free runners (5.86±1.9°, 6.25±3.5°, and 42.12±4.8° respectively). Abnormal movement proximally, has been theorized to result in compensations distally. Increased frontal plane pelvic motion has been described to contribute to increased valgus moments at the knee, further leading to increased stress upon the lower leg and the development of medial shin pain. Likewise, an increase in hip internal rotation ROM has been associated with an increase in tibial internal rotation ROM, again placing above average stress on the lower leg and contribute to the development of medial shin pain. Decreased knee flexion can decrease shock absorption during initial foot contact, sending the forces to the tibia and other musculoskeletal structures to be absorbed. Biomechanics of running gait

62 should be examined prospectively in runners with medial shin pain/MTSS to a cause/result relationship.

Tibial Stress Fractures. Stress injuries, such as stress fractures, most commonly occur in athletes as a result of excessive bone strain forming an accumulation of micro- damage, and simultaneously the inability to keep up with appropriate skeletal repair.(Hoch, Pepper, & Akuthota, 2005) Additionally, it is known that the muscles act as major shock absorbers during running, acting as protectors of the cortical bone.(Stanitski, McMaster, & Scranton, 1978) When muscles are working out of alignment or have less strength, the ability of the muscles to absorb shock is lessened during running, resulting in the transmission of force directly to the bones, increasing the accumulation of micro-damage.

Several factors contribute to this cycle and the development of tibial stress fractures in runners. Unlike general RRMIs, training related factors including training frequency and level of competition are not risk factors for tibial stress fractures.(Yagi et al., 2013) Rather other risk factor may be the primary source, and are exacerbated by running frequency and intensity. Researchers have identified that runners whom run in shoes older than 6 months are at an increased risk for a stress fracture, potentially due to the decrease in foam padding ability to absorb shock.(Gardner et al., 1988) Additionally, custom made orthotics provided to runners to place the foot in a neutral subtalar position did not have an impact on the overall incidence of stress fractures,(Ekenman et al., 2002) even though it did have an impact on the incidence rate in military recruits.(Finestone et al., 1999)

Other factors unique to playing a role in the development of stress fractures in females include low bone mineral density and menstrual irregularities. In a prospective studying examining all types of stress fractures sustained by runners over a 12 month period, female runners who developed a stress fracture had significantly lower total-body bone mineral content compared to female runners who did not sustain a stress fracture.(Bennell et al., 1996) When narrowing in on female runners who sustained tibial stress fractures, the bone mineral density of the tibia and fibula of the injured limb were significantly less than that of the matched limb in the female non-stress fracture group.

These findings were not significant for male runners. Lower bone mineral density may be an indicator of factors including inadequate dietary intake and ovary dysfunction.(Bennell et al., 1996) In addition, females who sustained a stress fracture had a significantly later age of menarche, and few menses in the year prior to the study.

Menstrual irregularities should be monitored in female athletes. Currently, research has not investigated the use of contraceptive pills to regulate the menstrual cycle in order to prevent stress fractures.

Retrospective evidence exists for differences in running kinematics between runners with tibial stress fractures and healthy runners. Peak rearfoot eversion and hip adduction angles during the stance phase of running have consistently been reported to be greater in runners with a previous history of a tibial stress fracture compared to healthy runners.(Pohl, Mullineaux, Milner, Hamill, & Davis, 2008) Peak rearfoot eversion was

2.7° greater in injured runners, as was peak hip adduction 3.5-4.0° compared to healthy runners.(Milner, Hamill, & Davis, 2010; Pohl et al., 2008) Researchers speculate that altered running mechanics may change the distribution of loads on the lower extremity,

64 predisposing runners to tibial stress fractures. Specifically, increased peak rearfoot eversion may lead to fatigue of the muscles of the deep posterior compartment of the calf responsible for controlling pronation. With fatigue, the inability of the muscles to absorb forces would be diminished placing increased tensile stress on the posteromedial tibia.

Training in a fatigued state has been shown to increase tensile strain on the medial tibia.(Milgrom et al., 2007; Pohl et al., 2008) It is conjectured that increase hip adduction may distribute forces on the lateral aspect of the tibia, thus placing compression forces laterally, and tensile forces on the medial tibia.(Pohl et al., 2008) Additionally, increased hip adduction may be the result of, or cause of increased peak rearfoot eversion, however this relationship has yet to be confirmed.

The prospective examination of kinematic risk factors for tibial stress fractures has yet to be conducted. On the other hand, hip abduction strength, which is theorized to control contralateral pelvic drop during running and furthermore the alignment of the lower extremities during running, has been investigated prospectively.(Yagi et al., 2013)

Isometric hip abduction strength was not different between high school runners who did and did not sustain a tibial stress fracture. However, running is an endurance sport, thus repetitive endurance testing or prolonged submaximal isometric strength should be used as a measurement rather than maximal isometric strength.

Iliotibial Band Syndrome. Iliotibial band friction syndrome (ITBS) is characterized as sharp pain or burning due to the posterior border of the iliotibial band

(ITB) impinging against the lateral femoral epicondyle.(Orchard, Fricker, Abud, &

Mason, 1996) Friction of the ITB against the bone occurs in approximately 30 degrees of knee flexion, occur at or just after foot strike during the stance phase of running.

Occasionally, swelling as well as thickening of the ITB at the site of friction can occur.

Pain has been reported to occur in runners with other activities of daily living, most commonly going up and down stairs as the knee goes in and out of flexion.

In a prospective examination of training variables, runners who developed ITBS reported a greater weekly mileage, reported performing more of their workouts on a track, and were less experienced than runners who remained healthy.(Messier et al.,

1995) Therefore, perhaps less experience runners were running too many miles per week.

Additionally, runners who participated in more swimming as a cross training activity were more likely to acquire ITBS. However, it is likely that excessive mileage, running surface and experience, and cross training activities are not the only contributors to ITBS, rather these variables interact with several others including muscular weaknesses and faulty running biomechanics.

Similar to other RRMI populations, it is postulated that irregular biomechanics can may result in an increased strain on the ITB leading to the development of

ITBS.(Fredericson et al., 2000) For example, the inability to control pelivc motion during the stance phase of running may cause a shift medially in the center of mass.(Foch &

Milner, 2014) The primary muscle responsible for controling contralateral pelvic drop is the hip abductor muscles, primarily the gluteus medius, which has been demonstrated to be weak in runners with ITBS compared to healthy runners.(Fredericson et al., 2000) To counteract this shift, the ipsilateral trunk musculature performs an ipsilateral trunk lean.

Thus it may be postulated that ipsilateral trunk muscular endurance may be stronger runners with ITBS. This theory has been tested using a case control study design and found that runners with ITBS had similar lateral core endurance using the side bridge test

66 compared to healthy runners.(Foch & Milner, 2014) However, investigators should rexamine this relationship using another testing method as the side bridge test can cause fatigue in the shoulder prior to the core, nullifying it’s measurement. Additionally, the

ITB acts as a stabilizer of the lateral hip, aimed at preventing excessive hip adduction.(Fredericson et al., 2000) When an unstable pelvis is present, it provides a weak foundation for the lower extrmity limbs. An increase in hip internal rotation and hip adduction can occur, placing increasing tensile strain on the ITB. Male runners with

ITBS do exhibit incresaed hip internal rotation during running, as well as decreased hip external rotation strength and a shortened ITB as measured with Ober’s test compared to healthy male runners.(Noehren, Schmitz, Hempel, Westlake, & Black, 2014) Excessive hip internal rotation could be the result of a shorter ITB, and weak hip external rotators.

Only one study to date has investigated prospectively joint kinematics in male runners.(Noehren, Davis, & Hamill, 2007) This study found that males runners that developed ITBS had an increased baseline peak hip adduction angle and peak knee internal rotation angle during the stance phase of running compared to male runners who remained healthy. Injured runners had 3.5° and 3.7° greater hip adduction and knee internal rotation, respectively, at peak during the stance phase of running. The ITB is strained when the hip moves into adduction, yet how this is related to hip abduction strength or possibly neuromuscular control has yet to me investigated prospectively. It can be theorized that the weakness in hip abduction strength seen in person with ITBS could be due to an increase in eccentric demand caused by excessive hip adduction, or that hip abduction weaknesses were present leading to increased hip adduction. The ITB has been reported to be one of the primary restraints against tibial internal rotation.(Terry,

Hughston, & Norwood, 1986) Thus, an increase in knee internal rotation, which was visible in male runners that developed ITBS, is theorized to shift the insertion of the ITB medially, placing more pressure on the lateral femroal condyle.

Patellofemoral Pain. Patellofemoral pain (PFP) is characterized as retropatellar pain that is exacerbated by activities with repetitious knee flexion and extension such as running, squatting, and ascending and descending stairs. Pain is thought to arise from the subchondral bone when the patella and femur make abnormal contact, due to misalignment of the patellofemoral joint.(Powers, 2010) Malalignment at the patellofemoral joint is thought to result from a contribution of both strength weaknesses and abnormal movement patterns in runners. Only one study has investigated hip muscular strength in runners with patellofemoral dysfunction syndrome (PFDS).(Thijs,

Pattyn, Van Tiggelen, Rombaut, & Witvrouw, 2011) The researchers measured isometric hip flexion and extension, internal and external rotation, and abduction and adduction strength in runners prior to participating in 10 week fix training schedule aimed to help participants complete a 5 kilometer race at the completion of the training program. There was no difference in any of the isometric hip strength measurements between 16 runners with PFDS and 16 healthy runners. However, it is important to note that the participants only received 15 seconds between trials, and it was not documented when randomizing whether some strength tests were back-to-back when they utilized the same muscle groups (ex: hip extension and external rotation). Strength weaknesses have been reported in individuals with PFP, that are not runners, such as 22% less hip abduction force, 21% less hip external rotation force,(Bolgla, Malone, Umberger, & Uhl, 2011) and 17% decreased hip extension force compared to healthy individuals.(Souza & Powers, 2009)

However, it was not stated how active these participants were, thus these findings may not apply to active, long distance endurance runners.

Retrospective case control studies suggest that misalignment may be in part due to faulty running mechanics. Increased peak hip adduction and internal rotation,(Wirtz,

Willson, Kernozek, & Hong, 2012) and knee internal rotation, have be exhibited in runners with PFP compared to healthy runners.(Noehren, Pohl, Sanchez, Cunningham, &

Lattermann, 2012) Differences of 2.2° of hip adduction, 4.6° hip internal rotation, and

3.5°. knee internal rotation have been reported. An increase in hip adduction angle creates a greater dynamic Q angle, and increases the contact pressure at the patellofemoral joint.

In addition, an increase hip internal rotation, rotates the femur laterally bringing the femur in closer contact with the patella, shifting the distribution of the forces at the patellofemoral joint laterally.(Li, DeFrate, Zayontz, Park, & Gill, 2004) In addition, runners have exhibited a trend towards increased contralateral pelvic drop (p=0.13) and decreased contralateral trunk lean (p=0.07).(Noehren et al., 2012) This indicates runners may counteract the medial shift in gravity from contralateral pelvic drop by leaning towards the stance limb. Only one prospective study to date has investigated evidence for a kinematic hip etiology for patellofemoral pain.(Noehren, Hamill, & Davis, 2013) The authors reported that over 2 years, 15 of 400 female runners were medically diagnosed with running-related PFP. The runners who developed PFP exhibited significantly greater peak hip adduction during the stance phase of running. No difference in peak hip internal rotation and rearfoot eversion was identified.

Long distance running is an endurance and fatiguing sport. Strength and kinematic changes related to fatigue can occur and may lead to the development of

RRMIs. In addition, changes in strength and kinematics have been reported to be exacerbated in females with PFP over the course of an exhaustive run.(Bazett-Jones et al.,

2013; Dierks, Manal, Hamill, & Davis, 2011) Over the course of an exhaustive run,

Dierks et al reported that al female runners, both with PFP and healthy, had significantly increased rearfoot eversion, and tibial internal rotation.(Dierks et al., 2011) There was a significant difference in knee flexion and hip adduction at the end of the run in the PFP runners compared to the healthy runners. The female runners with PFP had approximately 3.6° more knee flexion, and 3.2° more hip adduction compared to the healthy runners at the end of the exhaustive run. The female runners with PFP may have attempted to increase their knee flexion to reduce pain over the course of the run. Knee flexion helps to increase the ability to absorb ground reaction forces at impact. Research by Bazett-Jones et al the finding of increased knee flexion over the course of an exhaustive run, as well as reported an increase in hip flexion and anterior pelvic tilt in runners with PFP compared to healthy runners.(Bazett-Jones et al., 2013) In addition, the exhaustive run produced a significantly greater decrease in hip abduction and external rotation strength in runners with PFP compared to healthy runners. Again, kinematic changes post run may be a compensatory mechanism to reduce knee pain that can persist or worsen over the course of a prolonged run.

2.5 Conclusion

Demographic, health, and training related factors have been continually investigated as risk factors for RRMIs. At this time there exists minimal research as to whether musculoskeletal abnormalities and weaknesses, and an abnormal running gait

70 contribute prospectively to the development of RRMIs. Understanding the contribution of musculoskeletal factors to RRMIs is crucial to begin the development of clinical screening tests and prevention programs for clinicians, in turn leading to a decrease in the incidence rate of new RRMI and overall keeping runners active.

2.6 Research Line

2.6.1 Overall Goal

The overall goal of this research line is to reduce inactivity and disability associated with RRMIs. To attain this goal a series of steps including a variety of research designs will be utilized. Initially, retrospective case control studies will be utilized to examine new biomechanical, strength, and functional differences between runners with an injury of interest and healthy runners. These variables will then be utilized within prospective studies to determine if they are in fact risk factors. When risk factors are identified, randomized control trials for prevention and treatments to reduce risk of injury can be performed.

2.6.2 Alternative Goal

Because of the strong influence of previous injury history on RRMI risk, an alternative goal is to focus on intervention programs to rehabilitate runners that present with RRMIs. Developing programs that encompass gait retraining, strength increases, and functional movement performance improvement are key.

2.7 References

Alexander, C. J. (1990). Osteoarthritis: a review of old myths and current concepts.

Skeletal Radiol, 19(5), 327-333.

Bazett-Jones, D. M., Cobb, S. C., Huddleston, W. E., O’Connor, K. M., Armstrong, B. S.,

& Earl-Boehm, J. E. (2013). Effect of patellofemoral pain on strength and

mechanics after an exhaustive run. Med Sci Sports Exerc, 45(7), 133.

Bennell, K. L., Malcolm, S. A., Thomas, S. A., Reid, S. J., Brukner, P. D., Ebeling, P. R.,

& Wark, J. D. (1996). Risk factors for stress fractures in track and field athletes.

A twelve-month prospective study. Am J Sports Med, 24(6), 810-818.

Bennett, J. E., Reinking, M. F., Pluemer, B., Pentel, A., Seaton, M., & Killian, C. (2001).

Factors contributing to the development of medial tibial stress syndrome in high

school runners. J Orthop Sports Phys Ther, 31(9), 504-510.

Bolgla, L. A., Malone, T. R., Umberger, B. R., & Uhl, T. L. (2011). Comparison of hip

and knee strength and neuromuscular activity in subjects with and without

patellofemoral pain syndrome. Int J Sports Phys Ther, 6(4), 285-296.

Bovens, A. M., Janssen, G. M., Vermeer, H. G., Hoeberigs, J. H., Janssen, M. P., &

Verstappen, F. T. (1989). Occurrence of running injuries in adults following a

supervised training program. Int J Sports Med, 10 Suppl 3, S186-190.

Bredeweg, S. W., Buist, I., & Kluitenberg, B. (2013). Differences in kinetic asymmetry

between injured and noninjured novice runners: a prospective cohort study. Gait

Posture, 38(4), 847-852.

Buist, I., Bredeweg, S. W., Bessem, B., van Mechelen, W., Lemmink, K. A., & Diercks,

R. L. (2010a). Incidence and risk factors of running-related injuries during 72

preparation for a 4-mile recreational running event. Br J Sports Med, 44(8), 598-

604.

Buist, I., Bredeweg, S. W., Bessem, B., van Mechelen, W., Lemmink, K. A. P. M., &

Diercks, R. L. (2010b). Incidence and risk factors of running-related injuries

during preparation for a 4-mile recreational running event. Br J Sports Med,

44(8), 598-U530.

Buist, I., Bredeweg, S. W., Lemmink, K. A., van Mechelen, W., & Diercks, R. L. (2010).

Predictors of running-related injuries in novice runners enrolled in a systematic

training program: a prospective cohort study. Am J Sports Med, 38(2), 273-280.

Carmack, M. A., & Martens, R. (1979). Measuring commitment to running: a survey of

runners'attitudes and mental states. J Sport Psychol, 1, 25-42.

Cavanagh, P. R., & Lafortune, M. A. (1980). Ground reaction forces in distance running.

J Biomech, 13(5), 397-406.

CDC. (2012). Summary Health Statistics for U.S. Adults: National Health Interview

Survey, 2011. In E. J. Sondik, J. H. Madans & J. F. Gentleman (Eds.). Hyattsville,

Maryland: U.S Deparment of Health and Human Services.

Chan, C. S., & Grossman, H. Y. (1988). Psychological effects of running loss on

consistent runners. Percept Mot Skills, 66(3), 875-883.

Chang, W. L., Shih, Y. F., & Chen, W. Y. (2012). Running injuries and associated factors

in participants of ING Taipei Marathon. Phys Ther Sport, 13(3), 170-174.

Cheng, Y., Macera, C. A., Davis, D. R., Ainsworth, B. E., Troped, P. J., & Blair, S. N.

(2000). Physical activity and self-reported, physician-diagnosed osteoarthritis: is

physical activity a risk factor? J Clin Epidemiol, 53(3), 315-322.

Chorley, J. N., Cianca, J. C., Divine, J. G., & Hew, T. D. (2002). Baseline injury risk

factors for runners starting a marathon training program. Clin J Sport Med, 12(1),

18-23.

Clough, P. J., Shepherd, J., & Maughan, R. J. (1989). Marathon finishers and pre-race

drop-outs. Br J Sports Med, 23(2), 97-101.

Daoud, A. I., Geissler, G. J., Wang, F., Saretsky, J., Daoud, Y. A., & Lieberman, D. E.

(2012). Foot strike and injury rates in endurance runners: a retrospective study.

Med Sci Sports Exerc, 44(7), 1325-1334.

Dicharry, J. (2010). Kinematics and kinetics of gait: from lab to clinic. Clin Sports Med,

29(3), 347-364.

Dierks, T. A., Manal, K. T., Hamill, J., & Davis, I. (2011). Lower extremity kinematics in

runners with patellofemoral pain during a prolonged run. Med Sci Sports Exerc,

43(4), 693-700.

Dugan, S. A., & Bhat, K. P. (2005). Biomechanics and analysis of running gait. Phys

Med Rehabil Clin N Am, 16(3), 603-621.

Ekenman, I., Milgrom, C., Finestone, A., Begin, M., Olin, C., Arndt, T., & Burr, D.

(2002). The role of biomechanical shoe orthoses in tibial stress fracture

prevention. Am J Sports Med, 30(6), 866-870.

Ezzati, M., Hoorn, S. V., Rodgers, A., Lopez, A. D., Mathers, C. D., & Murray, C. J.

(2003). Estimates of global and regional potential health gains from reducing

multiple major risk factors. Lancet, 362(9380), 271-280.

Ferber, R., Hreljac, A., & Kendall, K. D. (2009). Suspected mechanisms in the cause of

overuse running injuries: a clinical review. Sports Health, 1(3), 242-246.

Finestone, A., Giladi, M., Elad, H., Salmon, A., Mendelson, S., Eldad, A., & Milgrom, C.

(1999). Prevention of stress fractures using custom biomechanical shoe orthoses.

Clin Orthop Relat Res, (360), 182-190.

Flegal, K. M., Carroll, M. D., Ogden, C. L., & Curtin, L. R. (2010). Prevalence and

trends in obesity among US adults, 1999-2008. JAMA, 303(3), 235-241.

Foch, E., & Milner, C. E. (2014). Frontal plane running biomechanics in female runners

with previous iliotibial band syndrome. J App Biomech, 30(1), 58-65.

Franz, J. R., Paylo, K. W., Dicharry, J., Riley, P. O., & Kerrigan, D. C. (2009). Changes

in the coordination of hip and pelvis kinematics with mode of locomotion. Gait

Posture, 29(3), 494-498.

Fredericson, M., Cookingham, C. L., Chaudhari, A. M., Dowdell, B. C., Oestreicher, N.,

& Sahrmann, S. A. (2000). Hip abductor weakness in distance runners with

iliotibial band syndrome. Clin J Sport Med, 10(3), 169-175.

Fredericson, M., & Misra, A. K. (2007). Epidemiology and aetiology of marathon

running injuries. Sports Med (Auckland, N.Z.), 37(4-5), 437-439.

Gardner, L. I., Jr., Dziados, J. E., Jones, B. H., Brundage, J. F., Harris, J. M., Sullivan, R.,

& Gill, P. (1988). Prevention of lower extremity stress fractures: a controlled trial

of a shock absorbent insole. Am J Public Health, 78(12), 1563-1567.

Giandolini, M., Poupard, T., Gimenez, P., Horvais, N., Millet, G. Y., Morin, J. B., &

Samozino, P. (2014). A simple field method to identify foot strike pattern during

running. J Biomech, 47(7), 1588-1593.

Glasser, W. (1976). Positive addiction. New York: Harper & Row.

Greist, J. H., Klein, M. H., Eischens, R. R., Faris, J., Gurman, A. S., & Morgan, W. P.

(1979). Running as treatment for depression. Compr Psychiatry, 20(1), 41-54.

Harrast, M. A., & Colonno, D. (2010). Stress fractures in runners. Clin Sports Med,

29(3), 399-416.

Henderson, J. (1976). The long run solution. Mountain View, CA: World Publications.

Hoch, A. Z., Pepper, M., & Akuthota, V. (2005). Stress fractures and knee injuries in

runners. Phys Med Rehabil Clin N Am, 16(3), 749-777.

Hogan, D. B., & Cape, R. D. (1984). Marathoners over sixty years of age: results of a

survey. J Am Geriatr Soc, 32(2), 121-123.

Hreljac, A., Marshall, R. N., & Hume, P. A. (2000). Evaluation of lower extremity

overuse injury potential in runners. Med Sci Sports Exerc, 32(9), 1635-1641.

Hubbard, T. J., Carpenter, E. M., & Cordova, M. L. (2009). Contributing factors to

medial tibial stress syndrome: a prospective investigation. Med Sci Sports Exerc,

41(3), 490-496.

Hunter, D. J., & Eckstein, F. (2009). Exercise and osteoarthritis. J Anat, 214(2), 197-207.

Jacobs, S. J., & Berson, B. L. (1986). Injuries to runners: a study of entrants to a 10,000

meter race. Am J Sports Med, 14(2), 151-155.

Jakobsen, B. W., Kroner, K., Schmidt, S. A., & Kjeldsen, A. (1994). Prevention of

injuries in long-distance runners. Knee Surg Sports Traumatol Arthrosc, 2(4),

245-249.

Jorgenson, C. B., & Jorgenson, D. E. (1979). Effect of Running on Perception of Self and

Others. Percept Mot Skills, 48, 242.

Karamanidis, K., & Arampatzis, A. (2005). Mechanical and morphological properties of

different muscle-tendon units in the lower extremity and running mechanics:

effect of aging and physical activity. J Exp Biol, 208(Pt 20), 3907-3923.

Kasmer, M. E., Liu, X. C., Roberts, K. G., & Valadao, J. M. (2013). Foot-strike pattern

and performance in a marathon. Int J Sports PhysiolPerform, 8(3), 286-292.

King, G. A., Fitzhugh, E. C., Bassett, D. R., Jr., McLaughlin, J. E., Strath, S. J., Swartz,

A. M., & Thompson, D. L. (2001). Relationship of leisure-time physical activity

and occupational activity to the prevalence of obesity. Int J Obes Relat Metab

Disord, 25(5), 606-612.

Kostrubala, T. (1977). The joy of running. New York: Simon & Schuster.

Kujala, U. M., Kettunen, J., Paananen, H., Aalto, T., Battie, M. C., Impivaara, O., . . .

Sarna, S. (1995). Knee osteoarthritis in former runners, soccer players, weight

lifters, and shooters. Arthritis and Rheum, 38(4), 539-546.

Lane, N. E. (1995). Exercise: a cause of osteoarthritis. J Rheum, 43, 3-6.

Lane, N. E., Michel, B., Bjorkengren, A., Oehlert, J., Shi, H., Bloch, D. A., & Fries, J. F.

(1993). The risk of osteoarthritis with running and aging: a 5-year longitudinal

study. J Rheumatol, 20(3), 461-468.

Lane, N. E., Oehlert, J. W., Bloch, D. A., & Fries, J. F. (1998). The relationship of

running to osteoarthritis of the knee and hip and bone mineral density of the

lumbar spine: a 9 year longitudinal study. J Rheum, 25(2), 334-341.

Larson, P., Higgins, E., Kaminski, J., Decker, T., Preble, J., Lyons, D., . . . Normile, A.

(2011). Foot strike patterns of recreational and sub-elite runners in a long-distance

road race. J Sports Sci, 29(15), 1665-1673.

Li, G., DeFrate, L. E., Zayontz, S., Park, S. E., & Gill, T. J. (2004). The effect of

tibiofemoral joint kinematics on patellofemoral contact pressures under simulated

muscle loads. J Orthop Res, 22(4), 801-806.

Lieberman, D. E., Venkadesan, M., Werbel, W. A., Daoud, A. I., D'Andrea, S., Davis, I.

S., & Pitsiladis, Y. (2010). Foot strike patterns and collision forces in habitually

barefoot versus shod runners. Nature, 463(7280), 531-535.

Lopes, A. D., Hespanhol Junior, L. C., Yeung, S. S., & Costa, L. O. (2012). What are the

main running-related musculoskeletal injuries? A Systematic Review. Sports

Med, 42(10), 891-905.

Loudon, J. K., Manske, R. C., & Reiman, M. P. (2013). Clinical Mechanics and

Kinesiology. Champaign, IL: Human Kinetics.

Loudon, J. K., & Reiman, M. P. (2012). Lower extremity kinematics in running athletes

with and without a history of medial shin pain. Int J Sports Phys Ther, 7(4), 356-

364.

Lun, V., Meeuwisse, W. H., Stergiou, P., & Stefanyshyn, D. (2004). Relation between

running injury and static lower limb alignment in recreational runners. Br J Sports

Med, 38(5), 576-580.

Lysholm, J., & Wiklander, J. (1987). Injuries in runners. Am J Sports Med, 15(2), 168-

171.

Macera, C. A. (1992). Lower extremity injuries in runners. Advances in prediction.

Sports Med, 13(1), 50-57.

Macera, C. A., Pate, R. R., Powell, K. E., Jackson, K. L., Kendrick, J. S., & Craven, T. E.

(1989). Predicting lower-extremity injuries among habitual runners. Arch Intern

Med, 149(11), 2565-2568.

Macera, C. A., Pate, R. R., Woods, J., Davis, D. R., & Jackson, K. L. (1991). Postrace

morbidity among runners. Am J Prev Med, 7(4), 194-198.

Macintyre, J. G., Taunton, J. E., Clement, D. B., Lloyd-Smith, D. R., McKenzie, D. C., &

Morrell, R. W. (1991). Running injuries: a clinical study of 4,173. Clin J Sports

Med, 1, 81-87.

Maehr, M. L., & Kleiber, D. A. (1981). The graying of achievement motivation. Am

Psychol, 36, 787-793.

Marti, B., Knobloch, M., Tschopp, A., Jucker, A., & Howald, H. (1989). Is excessive

running predictive of degenerative hip disease? Controlled study of former elite

athletes. BMJ (Clinical research ed.), 299(6691), 91-93.

Marti, B., Vader, J. P., Minder, C. E., & Abelin, T. (1988). On the epidemiology of

running injuries. The 1984 Bern Grand-Prix study. Am J Sports Med, 16(3), 285-

294.

Maughan, R. J., & Miller, J. D. (1983). Incidence of training-related injuries among

marathon runners. Br J Sports Med, 17(3), 162-165.

McDermott, M., & Freyne, P. (1983). Osteoarthrosis in runners with knee pain. Br J

Sports Med, 17(2), 84-87.

McKean, K. A., Manson, N. A., & Stanish, W. D. (2006). Musculoskeletal injury in the

masters runners. Clin J Sport Med, 16(2), 149-154.

Messier, S. P., Edwards, D. G., Martin, D. F., Lowery, R. B., Cannon, D. W., James, M.

K., & Hunter, D. M. (1995). Etiology of iliotibial band friction syndrome in

distance runners. Med Sci Sports Exerc, 27(7), 951-960.

Milgrom, C., Radeva-Petrova, D. R., Finestone, A., Nyska, M., Mendelson, S., Benjuya,

N., & Burr, D. (2007). The effect of muscle fatigue on in vivo tibial strains. J

Biomech, 40(4), 845-850.

Milner, C. E., Hamill, J., & Davis, I. S. (2010). Distinct hip and rearfoot kinematics in

female runners with a history of tibial stress fracture. J Orthop Sports Phys Ther,

40(2), 59-66.

Moen, M. H., Tol, J. L., Weir, A., Steunebrink, M., & De Winter, T. C. (2009). Medial

tibial stress syndrome: a critical review. Sports Med, 39(7), 523-546.

Morgan, W. P. (1979). Negative addiction in runners. Phys Sportsmed, 7, 56-63, 67-70.

Morgan, W. P., O'Connor, P. J., Sparling, P. B., & Pate, R. R. (1987). Psychological

characterization of the elite female distance runner. Int J Sports Med, 8 Suppl 2,

124-131.

Nicola, T. L., & Jewison, D. J. (2012). The anatomy and biomechanics of running. Clin

Sports Med, 31(2), 187-201.

Noehren, B., Davis, I., & Hamill, J. (2007). ASB clinical biomechanics award winner

2006 prospective study of the biomechanical factors associated with iliotibial

band syndrome. Clin Biomech, 22(9), 951-956.

Noehren, B., Hamill, J., & Davis, I. (2013). Prospective evidence for a hip etiology in

patellofemoral pain. Med Sci Sports Exerc, 45(6), 1120-1124.

Noehren, B., Pohl, M. B., Sanchez, Z., Cunningham, T., & Lattermann, C. (2012).

Proximal and distal kinematics in female runners with patellofemoral pain. Clin

Biomech, 27(4), 366-371.

Noehren, B., Schmitz, A., Hempel, R., Westlake, C., & Black, W. (2014). Assessment of

strength, flexibility, and running mechanics in men with iliotibial band syndrome.

J Orthop Sports Phys Ther, 44(3), 217-222.

Novacheck, T. F. (1998). The biomechanics of running. Gait Posture, 7(1), 77-95.

Ogden, C. L., Carroll, M. D., Kit, B. K., & Flegal, K. M. (2014). Prevalence of childhood

and adult obesity in the United States, 2011-2012. JAMA, 311(8), 806-814.

Orchard, J. W., Fricker, P. A., Abud, A. T., & Mason, B. R. (1996). Biomechanics of

iliotibial band friction syndrome in runners. Am J Sports Med, 24(3), 375-379.

Ounpuu, S. (1994). The biomechanics of walking and running. Clin Sports Med, 13(4),

843-863.

Pan, L., Blanck, H. M., Sherry, B., Dalenius, K., & Grummer-Strawn, L. M. (2012).

Trends in the prevalence of extreme obesity among US preschool-aged children

living in low-income families, 1998-2010. JAMA, 308(24), 2563-2565.

Panush, R. S., Hanson, C. S., Caldwell, J. R., Longley, S., Stork, J., & Thoburn, R.

(1995). Is running associated with osteoarthritis? An eight-year follow-up study. J

Clin Rheum, 1(1), 35-39.

Panush, R. S., & Lane, N. E. (1994). Exercise and the musculoskeletal system. Bailliere's

Clin Rheum, 8(1), 79-102.

Panush, R. S., Schmidt, C., Caldwell, J. R., Edwards, N. L., Longley, S., Yonker, R., . . .

Pettersson, H. (1986). Is running associated with degenerative joint disease?

JAMA, 255(9), 1152-1154.

Parker, D. T., Weitzenberg, T. W., Amey, A. L., & Nied, R. J. (2011). Group training

programs and self-reported injury risk in female marathoners. Clin J Sport Med,

21(6), 499-507.

Plisky, M. S., Rauh, M. J., Heiderscheit, B., Underwood, F. B., & Tank, R. T. (2007).

Medial tibial stress syndrome in high school cross-country runners: incidence and

risk factors. J Orthop Sports Phys Ther, 37(2), 40-47.

Pohl, M. B., Mullineaux, D. R., Milner, C. E., Hamill, J., & Davis, I. S. (2008).

Biomechanical predictors of retrospective tibial stress fractures in runners. J

Biomech, 41(6), 1160-1165.

Powers, C. M. (2010). The influence of abnormal hip mechanics on knee injury: a

biomechanical perspective. J Orthop Sports Phys Ther, 40(2), 42-51.

Robbins, J. M., & Joseph, P. (1980). Commitment to running: implications for the family

and work. Sociolocigal Symposium, 30, 87-108.

Rolland, Y., Abellan van Kan, G., & Vellas, B. (2010). Healthy brain aging: role of

exercise and physical activity. Clin Geriatr Med, 26(1), 75-87.

RRCA. (2013). Road Runners Club of America. Retrieved November 13, 2013, from

www.rrca.org.

RunningUSA. (2013a, April 21, 2013). 2013 State of the Sport - Part I: "Core Runner"

Profiles. Retrieved August 23, 2013, from

http://www.runningusa.org/index.cfm?fuseaction=news.details&ArticleId=1539&

returnTo=annual-reports.

RunningUSA. (2013b, July 28, 2013). 2013 State of the Sport - Part III: U.S. Race

Trends. Retrieved August 23, 2013, from http://www.runningusa.org/state-of-

sport-2013-part-III?returnTo=annual-reports.

Schache, A. G., Bennell, K. L., Blanch, P. D., & Wrigley, T. V. (1999). The coordinated

movement of the lumbo-pelvic-hip complex during running: a literature review.

Gait Posture, 10(1), 30-47.

Schache, A. G., Dorn, T. W., Blanch, P. D., Brown, N. A., & Pandy, M. G. (2012).

Mechanics of the human hamstring muscles during sprinting. Med Sci Sports

Exerc, 44(4), 647-658.

Schneider, S., Askew, C. D., Diehl, J., Mierau, A., Kleinert, J., Abel, T., & Struder, H. K.

(2009). EEG activity and mood in health orientated runners after different

exercise intensities. Physiol Behav, 96(4-5), 709-716.

Souza, R. B., & Powers, C. M. (2009). Differences in hip kinematics, muscle strength,

and muscle activation between subjects with and without patellofemoral pain. J

Orthop Sports Phys Ther, 39(1), 12-19.

Stanitski, C. L., McMaster, J. H., & Scranton, P. E. (1978). On the nature of stress

fractures. Am J Sports Med, 6(6), 391-396.

Summers, J. J., Machin, V. J., & Sargent, G. I. (1983). Psycho-social factors related to

marathon running. J Sport Psychol, 5(3), 314-331.

Summers, J. J., Sargent, G. I., Levey, A. J., & Murray, K. D. (1982). Middle-aged, non-

ellite marathon runners: a profile. Percept Mot Skills, 54, 963-969.

Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R., &

Zumbo, B. D. (2002a). A retrospective case-control analysis of 2002 running

injuries. Br J Sports Med, 36(2), 95-101.

Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R., &

Zumbo, B. D. (2003). A prospective study of running injuries: the Vancouver Sun

Run "In Training" clinics. Br J Sports Med, 37(3), 239-244.

Terry, G. C., Hughston, J. C., & Norwood, L. A. (1986). The anatomy of the iliopatellar

band and iliotibial tract. Am J Sports Med, 14(1), 39-45.

Thijs, Y., Pattyn, E., Van Tiggelen, D., Rombaut, L., & Witvrouw, E. (2011). Is hip

muscle weakness a predisposing factor for patellofemoral pain in female novice

runners? A prospective study. Am J Sports Med, 39(9), 1877-1882.

USA, S. M. S. (2012). 2012 Sports, Fitness and Leisure Activities Topline Participation

Report (pp. 44).

USA, S. M. S. (2013). 2013 Participation Report (P. A. Council, Trans.) (2013 ed., pp.

15). van Gent, R. N., Siem, D., van Middelkoop, M., van Os, A. G., Bierma-Zeinstra, S. M.,

& Koes, B. W. (2007). Incidence and determinants of lower extremity running

injuries in long distance runners: a systematic review. Br J Sports Med, 41(8),

469-480; discussion 480.

Van Middelkoop, M., Kolkman, J., Van Ochten, J., Bierma-Zeinstra, S. M., & Koes, B.

(2008). Prevalence and incidence of lower extremity injuries in male marathon

runners. Scand J Med Sci Sports, 18(2), 140-144.

84 van Poppel, D., Scholten-Peeters, G. G., van Middelkoop, M., & Verhagen, A. P. (2013).

Prevalence, incidence and course of lower extremity injuries in runners during a

12-month follow-up period. Scand J Med Sci Sports.

Walter, S. D., Hart, L. E., Mcintosh, J. M., & Sutton, J. R. (1989). The Ontario cohort

study of running-related injuries. Arch Intern Med, 149(11), 2561-2564.

Wen, D. Y., Puffer, J. C., & Schmalzried, T. P. (1998). Injuries in runners: a prospective

study of alignment. Clin J Sport Med, 8(3), 187-194.

WHO. (2009). Global health risks mortality and burden attributable to selected major

risks (W. H. Organization, Trans.) (pp. 1-70). Switzerland.

WHO. (2010). Global Recommendations on Physical Activity for Health (pp. 1-60).

Switzerland.

Wilks, D. C., Winwood, K., Gilliver, S. F., Kwiet, A., Chatfield, M., Michaelis, I., &

Rittweger, J. (2009). Bone mass and geometry of the tibia and the radius of

master sprinters, middle and long distance runners, race-walkers and sedentary

control participants: a pQCT study. Bone, 45(1), 91-97.

Williams, P. T. (1997a). Interactive effects of exercise, alcohol, and vegetarian diet on

coronary artery disease risk factors in 9242 runners: the National Runners' Health

Study. Am J Clin Nutr, 66(5), 1197-1206.

Williams, P. T. (1997b). Relationship of distance run per week to coronary heart disease

risk factors in 8283 male runners. The National Runners' Health Study. Arch

Intern Med, 157(2), 191-198.

Williams, P. T. (2007). Maintaining vigorous activity attenuates 7-yr weight gain in 8340

runners. Med Sci Sports Exerc, 39(5), 801-809.

Williams, P. T. (2008). Asymmetric weight gain and loss from increasing and decreasing

exercise. Med Sci Sports Exerc, 40(2), 296-302.

Williams, P. T. (2009a). Lower prevalence of hypertension, hypercholesterolemia, and

diabetes in marathoners. Med Sci Sports Exerc, 41(3), 523-529.

Williams, P. T. (2009b). Reduction in incident stroke risk with vigorous physical activity:

evidence from 7.7-year follow-up of the national runners' health study. Stroke; a

journal of cerebral circulation, 40(5), 1921-1923.

Williams, P. T. (2011). Exercise attenuates the association of body weight with diet in

106,737 runners. Med Sci Sports Exerc, 43(11), 2120-2126.

Williams, P. T. (2012a). Attenuating effect of vigorous physical activity on the risk for

inherited obesity: a study of 47,691 runners. PLoS One, 7(2), e31436.

Williams, P. T. (2012b). Non-exchangeability of running vs. other exercise in their

association with adiposity, and its implications for public health

recommendations. PloS one, 7(7), e36360.

Williams, P. T. (2013). Effects of running and walking on osteoarthritis and hip

replacement risk. Med Sci Sports Exerc, 45(7), 1292-1297.

Williams, P. T., Hoffman, K., & La, I. (2007). Weight-related increases in hypertension,

hypercholesterolemia, and diabetes risk in normal weight male and female

runners. Arterioscler Thromb Vasc Biol, 27(8), 1811-1819.

Williams, P. T., & Hoffman, K. M. (2009). Optimal body weight for the prevention of

coronary heart disease in normal-weight physically active men. Obesity, 17(7),

1428-1434.

Williams, P. T., & Thompson, P. D. (2013). Walking versus running for hypertension,

cholesterol, and diabetes mellitus risk reduction. Arterioscler Thromb Vasc Biol,

33(5), 1085-1091.

Williams, P. T., & Wood, P. D. (2006). The effects of changing exercise levels on weight

and age-related weight gain. Int J Obes, 30(3), 543-551.

Willick, S. (2001). Running and osteoarthritis. In F. O'Connor, R. Wilder & R. Nirschi

(Eds.), Textbook of Running Medicine (pp. 7). New York, NY: McGraw-Hill.

Willick, S. E., & Hansen, P. A. (2010). Running and osteoarthritis. Clin Sport Med,

29(3), 417-428.

Willson, J. D., Petrowitz, I., Butler, R. J., & Kernozek, T. W. (2012). Male and female

gluteal muscle activity and lower extremity kinematics during running. Clin

Biomech, 27(10), 1052-1057.

Wirtz, A. D., Willson, J. D., Kernozek, T. W., & Hong, D. A. (2012). Patellofemoral

joint stress during running in females with and without patellofemoral pain. Knee,

19(5), 703-708.

Yagi, S., Muneta, T., & Sekiya, I. (2013). Incidence and risk factors for medial tibial

stress syndrome and tibial stress fracture in high school runners. Knee Surg Sports

Traumatol Arthrosc, 21(3), 556-563.

Yuksel, O., Ozgurbuz, C., Ergun, M., Islegen, C., Taskiran, E., Denerel, N., & Ertat, A.

(2011). Inversion/Eversion strength dysbalance in patients with medial tibial

stress syndrome. J Sport Sci Med, 10(4), 737-742.

2.8 Tables

Table 2.1. Running related injury rates by anatomical site. Location Lysholm 1987 Bovens 1989 Walter 1989 Wen 1998 Taunton 2003 Buist 2010b Upper back NA 0.6% (1) Back 5.5% (3) 10.6% (79) 6.7% (6) 5.5% (11) Low back 5% Low Back 5.6% (9) (14) Hip/Pelvis 7.3% (4) 9% (16) 8.8% (66) 5.6% (5) 9.2% (23) 7.0% (14) Upper leg 6% Hamstring Upper Leg 18.2% (10) (11) 7.2% (54) 3.3% (3) 2.4% (6) 3.0% (6) Groin 2% (4) Thigh 1% (2) Knee 12.7% (7) 25% (43) 26.6% (199) 28.9% (26) 33.3% (83) 30.8% (62) Achilles/Calf Calf 6.0% (45) Calf 3.3% (3) 10.0% (25) Lower Leg 20.0% (11) 21% (37) 33.3% (67) Shin 21.1% Shin 14.6% Shin 6.0% (45) (19) (38) Ankle 14.5% Ankle 12% (21) (8) Ankle 15.1% (112) 10.0% (9) 10.4% (26) 5.5% (11) Achilles 9.1% Achilles 11% (5) (19) Foot 12.7% (7) 6% (10) 15.7% (117) 21.1% (19) 13.2% (33) 3.9% (8) Other NA 1.6% (2) 4.0% (30) NA NA 10.9% (22)

Table 2.2. Top five specific running-related injury diagnoses.

Incidence Rates Prevalence Rates

Lysholm and Jakobsen et al Macintyre et al Taunton et al McKean et al. Rank Wiklander 1987 1994 1991 2002 2006 Medial Tibial Medial Tibial Patellofemoral Patellofemoral Plantar Fasciitis 1 Stress Syndrome Stress Syndrome Pain Pain Syndrome 17.5% (495) 14.5% (8) 20% (4) 24.3% (573) 16.5% (331) Iliotibial Band Iliotibial Band Hamstring Strains Ankle Sprain Patellar Tendinitis 2 Friction Syndrome Friction Syndrome 10.9% (6) 15.0% (3) 12.5% (353) 7.2% (170) 8.4% (168) Hamstrings Ankle Sprain Achilles Tendinitis Plantar Fasciitis Plantar Fasciitis 3 Tendinopathy 10.9% (6) 10.0% (2) 5.2% (123) 7.9% (158) 12.5% (353) Muscle Fibre Iliotibial Band Achilles Tendinitis Patellar Tendinitis Meniscal Injuries 4 Rupture Syndrome 10.9% (6) 5.1% (120) 5.0% (100) 10.0% (2) 10.5% (297) Achilles Tendinitis Hamstring 4.7% (111) Tibial Stress Achilles Runners Knee 5 Tendinitis Tibial Stress Syndrome Tendinopathy 10.0% (2) 7.3% (4) Syndrome 4.9% (99) 9.5% (268) 4.7% (111)

2.9 Figures

60 51.45 50

28.56 30 23.71

20 11.65 12.99 9.18 10 6.22 1.89

0 US Participants US Age Years 6 Moreor(millions)

Physical Activity

Figure 2-1. Participation across various physical activities.

2012

2011

2010

2005 Year 2000

1995

1990

- 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 Number of Americans (millions)

Male Female

Figure 2-2. U.S. running event finishers.

Half-Marathon 35.60% 39.90% 10K Marathon

Others

3.10% 9.50% 11.90%

Figure 2-3. Finishers in U.S running events in 2012.

Reduce inactivity and disability associated with RRMIs

Prevention Intervention

Randomized Control Case Control Studies Prospective Studies Gait Retraining Trials

Biomechanical Screening Tools Strength Programs

Functional Movement Strength Prevention Programs Programs

Functional

Figure 2-4. Research line schematic.

Chapter 3

Running Biomechanics in Injured and Injury Free Runners Participating in a “Marathon in Training” Program: A Prospective Cohort Study

3.1 Abstract

Purpose: To compare baseline running biomechanics of the hip, pelvis, and trunk during the stance phase of running, between female runners who sustain a RRMI during a

“marathon in training” program and runners who remain injury-free. Methods: Three- dimensional kinematics and kinetics were collected in fifty-four female runners while running over ground. Hip, pelvic, and trunk frontal plane kinematics, and hip transverse plane kinematics during the stance phase of running were extracted and reported as means and 90% confidence intervals for both the RRMI and injury free (INJF) groups.

Areas in which the confidence intervals did not cross for three consecutive percentage points of the stance phase of running were pinpointed. Results: The RRMI group exhibited increased contralateral pelvic drop and increased contralateral trunk lean during the stance phase of running compared to the INJF group. For hip frontal and transverse plane kinematics there were no time points during the stance phase of running that the

93 confidence intervals did not overlap. Conclusion: Baseline differences in running kinematics were observed between the RRMI and INJF groups. The RRMI group compared to the INJF group presented with increased contralateral pelvic drop and trunk lean for 57% and 87% of the stance phase of running, respectively. This finding indicates that these exaggerated running mechanics may be related to the development of a RRMI amongst female runners during training. Clinicians and researchers should utilize gait analysis to identify biomechanical alterations in runners, and implement appropriate intervention strategies such as gait reeducation and strengthening to minimize frontal plane pelvic motion during running. Keywords: running biomechanics, running related musculoskeletal injury.

3.2 Introduction

In 2012 it was estimated that approximately 51.5 million Americans participated in running or jogging.(USA, 2013) Individuals choose to run as a means to maintain or improve their fitness level, and advance or preserve their physical and psychological health.(Summers, Machin, & Sargent, 1983) When compared to other sports, the direct benefits of running are substantial, including greater weight control leading to a significant reduction in body mass index and abdominal body circumference(Williams,

2012) and a reduced risk for the development of hip osteoarthritis and hip replacement.(Williams, 2013) Despite the plethora of positive outcomes of running, running related musculoskeletal injuries (RRMI) present one potential undesirable and deleterious outcome.

Researchers estimate that anywhere from 15-83% of all varieties of runners sustain a RRMI annually.(Bredeweg, Buist, & Kluitenberg, 2013; van Gent et al.,

2007)Across runners of all ages and training levels, the top three reported RRMIs diagnosed in a sports medicine clinic were patellofemoral pain syndrome (PFPS), iliotibial band syndrome (ITBS), and plantar fasciitis.(Taunton et al., 2002) The etiology of RRMIs are multifactorial, with investigated factors divided into four categories: systemic, running/training related, health, and lifestyle factors.(van Gent et al., 2007)

Regardless of their contribution to a RRMI, systemic factors such as age, sex, height, and lower extremity alignment, and health factors such as a history of a previous injury cannot be changed. Training related errors that place runners at risk for an RRMI such as an increase in training distance per week can be modified, but is at the discretion of the runner.(Satterthwaite, Norton, Larmer, & Robinson, 1999; Wen, Puffer, & Schmalzried,

1998) There remains a void in research to identify clinically modifiable risk factors for

RRMIs, such as range of motion, strength, neuromuscular control and running kinematics. Factors such as these could be addressed in a pre-participation screening, and modified or corrected when deficiencies are detected.

Running is an endurance sport involving repetitive ground contact over an extended period of time. If a runner presents with an altered trunk or lower extremity running gait it can be detrimental to the additional areas in the musculoskeletal system.

When dysfunction occurs proximally, abnormal stress can be placed on distal structures, overtime resulting in damage and leading to a painful RRMI. Thus, kinematic variables such as joint angles during running have been investigated between runners with a RRMI and healthy runners. However, due to the multifactorial nature of RRMIs, researchers

95 have chosen to investigate the biomechanical factors influencing individual RRMIs, such as PFPS, ITBS, medial tibial stress syndrome (MTSS) and tibial stress fractures (TSFX) separately. Retrospectively, researchers have identified proximal factors at the core that are present in runners with distal RRMIs, including increased hip adduction(R. Ferber,

Noehren, Hamill, & Davis, 2010; Noehren, Pohl, Sanchez, Cunningham, & Lattermann,

2012; Willson & Davis, 2008) and internal rotation angles (Loudon & Reiman, 2012;

Noehren et al., 2012) increased contralateral pelvic drop (Loudon & Reiman, 2012) and a trend towards increased ipsliateral trunk lean during the stance phase of running gait.

(Noehren et al., 2012) Only two studies have been conducted prospectively investigating the contribution of altered running biomechanics towards the development of PFPS

(Noehren, Hamill, & Davis, 2013) and ITBS (B. Noehren, Davis, & Hamill, 2007) amongst runners. The authors identified increased hip adduction angle during the stance phase of running to be a contributing factor to the development of both PFPS and ITBS.

Due to the location of PFPS, ITBS, MTSS, and TSFX distally from the hip, as well as a plethora of other RMMIs at or below the knee, perhaps altered running gait proximally is a contributing factor for many RRMIs and therefore should be investigated as a single cohort.

The purpose of this prospective study was to compare hip, pelvic, and trunk running biomechanics between female runners who sustained a RRMI and runners who remained injury free while participating in a “marathon in training” program. It was hypothesized that runners who sustained a RRMI would exhibit increased hip adduction and internal rotation, contralateral pelvic drop, and ipsilateral trunk lean compared to the injury free group.

3.3 Methods

3.3.1 Study Design

This study was a prospective cohort, in which a single group of female runners were tested at baseline and tracked over a 16 week “marathon in training” program. Our independent variable was group (RRMI and injury free [INJF]), which was determined at the end of the program. The dependent variables were running kinematics, specifically trunk, pelvis, and hip frontal plane kinematics and hip transverse plane kinematics during the stance phase of running.

3.3.2 Participants

Female participants enrolled in a “marathon in training” program organized by a local running store were examined prior to the start of the program. Gender differences in running have been reported,(Reed Ferber, Davis, & Williams Iii, 2003) requiring the investigation of running biomechanics as a contributing factor to the development of a

RRMI in females separately. Female runners were excluded from this study if they had a previous RRMI or other non-RRMI injury of the lower extremity or back within the past

6 months, or were currently pregnant or breastfeeding. Prior to participation in the study, all individuals provided written informed consent (Appendix A). The study protocol was approved by the institution’s review board.

3.3.3 Instrumentation

Kinematic and kinetic data were collected using a 12 camera motion analysis system (Motion Analysis Corporation) operating at a sampling frequency of 200 Hz, and an AMTI force plate (Advanced Mechanical Technology Inc., Watertown, MA) operating at a sampling frequency of 1000Hz was synchronized with the motion capture system.

3.3.4 Procedures

Before the outset of the “marathon in training” program, participants attended a baseline testing session in which each individual’s bilateral running biomechanics were measured. In addition, participants completed questionnaires providing information pertaining to their injury and running history (Appendices B-F).

(ASIS), greater trochanter, lateral thigh, anterior-distal thigh, lateral and medial femoral condyles, tibial tuberosity, lateral shank, medial and lateral malleolus, heel, first and fifth metatarsal heads, navicular bone, and second toe, as well as the manubrium, seventh cervical spinous process, and right scapula. Participants stood in the lab coordinate space with feet shoulder width apart, facing the direction of the dynamic running trials. A static trial was collected for 3 seconds to allow for the creation of a 3D model for each participant during data processing. Following the static calibration trial, anatomical markers on the iliac crest, medial femoral condyles, medial malleoli, and first and fifth 98 metatarsal heads were removed. The marker set was a modified version of that used previously.(Salsich & Long-Rossi, 2010)

Participants were given as many practice trials as necessary to become familiar with their speed and environment while running over ground. Running trials were performed along a 15 meter runway at a self-selected pace. A self-selected pace was utilized over a standard pace due to the highly varied paces of runners participating in this study. In addition, RRMIs more commonly occur during training at a self-selected pace, thus the self-selected pace mirrored the participant’s normal training habits.(Miller,

Lowry, Meardon, & Gillette, 2007) Running velocity was monitored using timing gaits

(Brower Timing Systems, Utah) placed 1.8 meters apart along the runway surrounding the forceplate. A tester monitored the participant’s foot strike to ensure the foot was contacting the force plate in its entirety, and then moved the participant forwards or backwards from her starting position based on the foot strike to enable her to successfully strike the force plate with her entire foot. Six successful trials of running overground were collected for both limbs, for each individual participant. A successful trial was defined as the foot contacting the force plate in its entirety, and not speeding up or slowing down as she approached the force plate. Speed when approaching the force plate was monitored using the velocity of the sacral marker. The starting limb was randomized for each participant.

3.3.5 “Marathon in Training” Program

The formalized “marathon in training” program was sixteen weeks in length, and prepared participants for either a half or full marathon at the conclusion of the program.

All participants followed one of four training plans: beginner-half marathon, beginner- full marathon, advanced-half marathon, and advanced-full marathon. All programs were designed by a USA Track and Field Level 2 Endurance Coach. Over the course of the program, participants met biweekly for a speed workout and a long run. All group runs were under the supervision of 16 coaches of varying experience. On their own participants ran an additional 3 or 4 days as determined by the training plan the participant chose. All workouts were documented on a weekly log that included activity time, distance and pace.

3.3.6 Injury Tracking

Throughout the sixteen week program, participants reported any RRMIs to the lead investigator. If injured, a participant had the option to see her own physician or physical therapist, or to see the certified athletic trainer or physical therapist involved in this study. If the participant saw her own healthcare practitioner, an injury form was completed by the clinician and returned to the lead investigator. If the participant sought treatment from the physical therapist involved in the present study, he filled out the form and returned it to the lead investigator (Appendix G). The injury form extracted information from the participant including location of injury, date of injury, description of pain, pain during various activities graded on a 100 point visual analog scale, treatment to date, and any alterations to training program if any. The physician or physical therapist performed an evaluation and documented if the injury was a RRMI.

The definition of an RRMI utilized in this prospective cohort study was any chronic, running related, musculoskeletal injury of the lower extremity or back that

100 resulted in the participant seeking out a clinician and prompted one of the following: 1) modified or halted their running participation for at least one planned training day, including deviations in speed, time, or distance; or 2) performed an alternate, less demanding activity in replace of running for at least one planned, training day, including but not limited to biking, swimming or working out on an elliptical trainer.

3.3.7 Data Processing

Hip, pelvic and trunk kinematics, and ground reaction forces (GRF) for each running trial were calculated using Visual3D software (C-Motion Inc, Rockville, MD).

Joint kinematics of the right limb, and transformed data of the left limb were defined using the right hand rule. The kinematic variables of interest were frontal plane motion of the trunk (contralateral and ipsilateral trunk lean), pelvis (contralateral pelvic drop and lift), and hip (abduction and adduction), and transverse plane motion of the hip (external and internal rotation) during the stance phase of each running trial. Kinematic and kinetic data were low-pass filtered at 12Hz and 50Hz, respectively, with a fourth-order zero lag

Butterworth filter.(Bazett-Jones et al., 2013)

The stance phase was determined using the vertical ground reaction force (vGRF).

Foot strike and toe off we defined as the point in which the vGRF went above and below

20N, respectfully. All running biomechanical data was normalized across the stance phase (100 time points) and averaged for each participant.

101

3.3.8 Statistical Analysis

For all statistical analyses the independent variable was group (RRMI and INJF).

For all comparisons, the injured limb of the RRMI group was compared with the average of the limbs of the INJF group. The dependent variables of interest were frontal plane hip, pelvic and trunk motion, and hip transverse plane motion during the stance phase of running gait. Throughout the individual planes of motion, RRMI and INJF group means and associated 90% confidence intervals were calculated.(Hopkins, Marshall, Batterham,

& Hanin, 2009) All 100 time points were inspected for sections in which the confidence intervals did not overlap for three consecutive time points, which was considered to be statistically significant. (Chinn, Dicharry, & Hertel, 2013)

3.4 Results

A total of fifty-six female participants were recruited with an average age, height and mass of 39 years (standard deviation, SD ± 9), 1.66 meters (SD ± 0.08), and 66.76 kilograms (SD ± 13.32) respectfully. Three participants were excluded from analysis due to equipment error (n=2), and because the participant was briskly walking and not running (n=1). Additionally, three runners sustained acute ankle sprains and were removed from analysis as the present study was interested in chronic RRMIs.

3.4.1 Running Related Musculoskeletal Injuries

Fifteen female runners sustained an RRMI during the “marathon in training” program, leaving 35 female runners injury-free at the conclusion of the program. Group

102 demographics are reported in Table 3.1. Of the RRMIs, 8 occurred at the knee joint, 4 occurred in the foot/ankle, and one each occurred at the hip, thigh, and calf.

3.4.2 Running Biomechanics

Running speed was not significantly different between groups (RRMI

2.83±0.20m/s, INJ 2.71±0.30m/s; p=0.14). The RRMI group demonstrated 1.44±0.08° greater contralateral pelvic drop compared to the INJF group between 16% and 28% of the stance phase of running, and 1.64±0.12° greater contralateral pelvic drop from 48% to

93% of the stance phase of running (Figure 3-1). The RRMI group demonstrated

1.19±0.07°decreased ipsilateral trunk lean compared to the INJF group between 1% and

87% of the stance phase of running (Figure 3-2). For hip frontal plane and transverse plane movement, there were no increments during the stance phase of running that the

90% confidence intervals did not overlap (Figures 3-3 & 3-4).

3.5 Discussion

The purpose of this study was to identify differences in trunk, pelvic, and hip running biomechanics from a baseline testing session between female runners who went on to sustain an RRMI during training and runners who remained injury free. The principal finding of this investigation is that there were kinematic differences in frontal plane pelvic and trunk motion during the stance phase of running between the RRMI and

INJF groups. To our knowledge, this is the first study to evaluate running biomechanical differences prospectively between runners who sustained an RRMI during training and runners who remained injury-free.

103

The overall incidence rate of RRMIs in this study was 30% (n=15). Previous prospective studies have reported rates to be 19.4 to 79. %.(van Gent et al., 2007) The few studies that have utilized participants within a GTP are around 16.2-

29.5%.(Bredeweg et al., 2013; Buist, Bredeweg, Bessem, et al., 2010; Taunton et al.,

2003) However, these studies examined males and females collectively. When separating out females only the rates were between 17.3 and 30.2%. Our rate of 30% was closest to that by Taunton et al 2003 which utilized a 13 week program and provided two training plans to cater to a variety of runners; whereas the present studies was 16 weeks in length and provided four training plans.(Taunton et al., 2003) Compared with studies that utilized programs 8 and 9 weeks in length, their reported rates of 23.2% and 17.3%, respectively were lower than the present study.(Bredeweg et al., 2013; Buist, Bredeweg,

Lemmink, van Mechelen, & Diercks, 2010) Additional differences between studies could be in part due to the definition of a RRMI, as well as how the injury information was collected. The present study utilized a definition in which the RRMI impacted at least one day of participation, compared to Bredweg et al. 2013 whom utilized a time of 1 week, which could explain a lower overall RRMI rate at 16.2%. Lastly, like the present prospective study, researchers should utilize a healthcare professional to diagnose injuries instead of self-reporting injuries by participants via online or paper questionnaires.

(Bredweg et al. 2013)

Researchers have investigated the running mechanics of runners with RRMIs compared to injury free runners using retrospective studies, in which altered running biomechanics of the hip and trunk have been identified, specifically an increase in hip adduction(R. Ferber et al., 2010; Noehren et al., 2012; Willson & Davis, 2008) and

104 internal rotation (Loudon & Reiman, 2012; Noehren et al., 2012) and contralateral pelvic drop (Loudon & Reiman, 2012) and a trend towards increased ipsliateral trunk lean.(Noehren et al., 2012) These altered running mechanics could lead towards a medial collapse of the limb, placing stresses at the knee, shin, ankle and foot. Repetitive stress with malalignment of the lower extremity during an extended bout of running could result in an abnormal stress on tissues poorly adapted to it, resulting in injury. However, it has yet to be determined if the changes in running kinematics are a result of, or a predisposing factor for a RRMI.

The results of the present study show altered running kinematics in the RRMI group compared to the INJF group at the baseline testing session, suggesting that increased contralateral pelvic drop and contralateral trunk lean during the stance phase of running may contribute to the development of a RRMI in female runners. Throughout the gait cycle the pelvis remains relatively stable, while the hip adducts relative to the pelvis, acting as a shock absorbing mechanism.(Novacheck, 1998) An increase in contralateral pelvic drop was observed in the RRMI group compared to the INJF group during the stance phase of running, specifically from 16% to 28%, and 48% to 93% of stance phase.

An increase in contralateral pelvic drop, without an increase in hip adduction could mean the hip abductors are not involved and instead the quadratus lumborum (QL) is playing a role in altered kinematics. The QL acts as both a lumbar vertebrae stabilizer (medial portion) and a lateral trunk flexor (lateral portion).(Richardson, Jull, Hodges, Hides, &

Panjabi, 1999) However, when in an open chain position, similar to the swing limb during running, the QL can then act as an ipsilateral pelvic lifter, or to resist pelvic drop.

Perhaps the QL is attempting to control the pelvis during running, thus resulting in an

105 apparent increased contralateral pelvic drop, while not impacting the hip joint.

Neuromuscular activity of the core musculature was not examined in the present study, thus we cannot determine if the QL played a role in pelvic biomechanics in the present study. Future research should investigate QL neuromuscular control compared to the gluteus medius and other core muscles in runners.

Female runners in the RMMI group also demonstrated an increase in contralateral trunk lean during the stance phase of running compared to the INJF group, specifically throughout the first 87% of the stance cycle. The trunk, pelvis, and hips are closely coordinated throughout the gait cycle as a means to minimize the transfer of lower extremity motion towards the shoulders and head, as well as to maintain lateral balance and equilibrium.(Schache, Bennell, Blanch, & Wrigley, 1999) The RRMI group could be demonstrating an increase in lower extremity movement, which is being transferred to the upper body. When the upper body moves more, an increase in shifting of the center of gravity could result in the leaning of the body to one side or the other. During the stance phase, when the body leans to the contralateral side, the ipsilateral QL may have to activate further to pull the limb from going too far laterally, stopping the lateral shift in gravity away from the stance limb. Presented only as a theory, research should investigate the neuromuscular control of the core musculature including the QL, gluteus medius, lumbar multifidi, and abdominal muscles, in conjunction with the distribution of the center of mass during running.

There were no baseline differences in hip frontal or transverse plane kinematics between runners who sustained an RRMI and INJF runners. Researchers have investigated prospectively the influence of running biomechanics at the hip on the

106 development of individual RRMIs.(Noehren et al., 2013; B. Noehren et al., 2007) In particular, the runners who developed PFP and ITBS in these prospective studies, exhibited approximately 3.5 to 4 degrees more hip adduction, compared to the injury free group. However, consistent with the findings of the present study there were no differences between the PFP group and the injury free group for hip internal rotation during running.

Although the results are intriguing, there are a few limitations that need to be acknowledged. First, only hip, pelvis and trunk kinematics during running were investigated within the participants. Researchers have identified retrospectively differences in running kinematics at the knee and ankle complex within specific RRMI populations. Additionally, although the objective of this study was to investigate the impact of running kinematics on the development of an RRMI, the literature has identified several other risk factors that should be examined concurrently. Additionally, due to the wide range of participants enrolling in the “marathon in training” program, and thus enrolling in the present study, participants running biomechanics were analyzed using a self-selected pace over a standard speed. A self-selected speed was chosen over a standard speed as the RRMIs of interest were chronic, overuse injuries which are likely to develop when performing ones typical, every day running pattern. A standard speed, typically around 3.7m/s or 7:14 min/mile may have been too fast and uncomfortable for the majority of our participants who averaged 2.7m/s or 9:50min/mile. The repeatability of lower extremity running kinematics and kinetics using a standard speed and self- selected speed has been investigated, of which the self-selected speed produced better consistency.(Queen, Gross, & Liu, 2006) Running speed has been shown to have no

107 effect on the repeatability of measuring running kinematics. Lastly, this study only investigated female runners; future research should similarly investigate the influence of running biomechanics on male runners.

3.6 Conclusion

The results of this prospective study reveal that female runners who present with altered running biomechanics, specifically increased contralateral pelvic drop and decreased ipsilateral trunk lean, could be predisposed to the development of an RRMI during training. Clinicians should perform a thorough orthopedic evaluation, including an analysis of running technique to provide feedback and interventions to address potential abnormal findings, with the goal of preventing a RRMI.

108

3.7 References

Bazett-Jones, D. M., Cobb, S. C., Huddleston, W. E., O’Connor, K. M., Armstrong, B. S.,

& Earl-Boehm, J. E. (2013). Effect of patellofemoral pain on strength and

mechanics after an exhaustive run. Med Sci Sports Exerc, 45(7), 133.

Bredeweg, S., Buist, I., & Kluitenberg, B. (2013). Differences in kinetic asymmetry

between injured and noninjured novice runners: A prospective cohort study. Gait

Posture, 38(4), 847-852.

Buist, I., Bredeweg, S. W., Bessem, B., van Mechelen, W., Lemmink, K. A. P. M., &

Diercks, R. L. (2010). Incidence and risk factors of running-related injuries during

preparation for a 4-mile recreational running event. Br J Sports Med, 44(8), 598-

U530.

Buist, I., Bredeweg, S. W., Lemmink, K. A. P. M., van Mechelen, W., & Diercks, R. L.

(2010). Predictors of running-related injuries in novice runners enrolled in a

systematic training program a prospective cohort study. Am J Sports Med, 38(2),

273-280.

Chinn, L., Dicharry, J., & Hertel, J. (2013). Ankle kinematics of individuals with chronic

ankle instability while walking and jogging on a treadmill in shoes. Phys Ther

Sport, 14(4), 232-239.

Ferber, R., Davis, I. M., & Williams Iii, D. S. (2003). Gender differences in lower

extremity mechanics during running. Clin Biomech, 18(4), 350-357.

Ferber, R., Noehren, B., Hamill, J., & Davis, I. (2010). Competitive female runners with

a history of iliotibial band syndrome demonstrate atypical hip and knee

kinematics. J Orthop Sports Phys Ther, 40(2), 52-58. 109

Hopkins, W., Marshall, S., Batterham, A., & Hanin, J. (2009). Progressive statistics for

studies in sports medicine and exercise science. Med Sci Sports Exerc, 41(1), 3.

Loudon, J. K., & Reiman, M. P. (2012). Lower extremity kinematics in running athletes

with and without a history of medial shin pain. Int J Sports Phys Ther, 7(4), 356-

364.

Miller, R. H., Lowry, J. L., Meardon, S. A., & Gillette, J. C. (2007). Lower extremity

mechanics of iliotibial band syndrome during an exhaustive run. Gait Posture,

26(3), 407-413.

Noehren, Hamill, J., & Davis, I. (2013). Prospective evidence for a hip etiology in

patellofemoral pain. Med Sci Sport Exer, 45(6), 1120-1124.

Noehren, Pohl, M. B., Sanchez, Z., Cunningham, T., & Lattermann, C. (2012). Proximal

and distal kinematics in female runners with patellofemoral pain. Clin Biomech,

27(4), 366-371.

Noehren, B., Davis, I., & Hamill, J. (2007). Prospective study of the biomechanical

factors associated with iliotibial band syndrome. Clin Biomech, 22(9), 951-956.

Novacheck, T. F. (1998). The biomechanics of running. Gait Posture, 7(1), 77-95.

Queen, R. M., Gross, M. T., & Liu, H.-Y. (2006). Repeatability of lower extremity

kinetics and kinematics for standardized and self-selected running speeds. Gait

Posture, 23(3), 282-287.

Richardson, C., Jull, G., Hodges, P., Hides, J., & Panjabi, M. M. (1999). Therapeutic

exercise for spinal segmental stabilization in low back pain: scientific basis and

clinical approach: Churchill Livingstone Edinburgh.

110

Salsich, G. B., & Long-Rossi, F. (2010). Do females with patellofemoral pain have

abnormal hip and knee kinematics during gait? Physiother Theory Pract, 26(3),

150-159.

Satterthwaite, P., Norton, R., Larmer, P., & Robinson, E. (1999). Risk factors for injuries

and other health problems sustained in a marathon. Br J Sports Med, 33(1), 22-26.

Schache, A. G., Bennell, K. L., Blanch, P. D., & Wrigley, T. V. (1999). The coordinated

movement of the lumbo–pelvic–hip complex during running: a literature review.

Gait Posture, 10(1), 30-47.

Summers, J. J., Machin, V. J., & Sargent, G. I. (1983). Psychosocial factors related to

marathon running. J Sport Psychol, 5(3), 314-331.

Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R., &

Zumbo, B. D. (2002). A retrospective case-control injuries analysis of 2002

running. Br J Sports Med, 36(2), 95-101.

Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R., &

Zumbo, B. D. (2003). A prospective study of running injuries: the Vancouver Sun

Run "In Training" clinics. Br J Sports Med, 37(3), 239-244.

USA, S. M. S. (2013). 2013 Participation Report (P. A. Council, Trans.) (2013 ed., pp.

15). van Gent, R. N., Siem, D., van Middelkoop, M., van Os, A. G., Bierma-Zeinstra, S. M.,

& Koes, B. W. (2007). Incidence and determinants of lower extremity running

injuries in long distance runners: a systematic review. Br J Sports Med, 41(8),

469-480; discussion 480.

111

Wen, D. Y., Puffer, J. C., & Schmalzried, T. P. (1998). Injuries in runners: a prospective

study of alignment. Clin J Sport Med, 8(3), 187-194.

Williams, P. T. (2012). Non-exchangeability of running vs. other exercise in their

association with adiposity, and its implications for public health

recommendations. Plos One, 7(7), e36360.

Williams, P. T. (2013). Effects of running and walking on osteoarthritis and hip

replacement risk. Med Sci Sports Exerc, 45(7), 1292.

Willson, J. D., & Davis, I. S. (2008). Lower extremity mechanics of females with and

without patellofemoral pain across activities with progressively greater task

demands. Clin Biomech, 23(2), 203-211.

112

3.8 Tables

Table 3.1. Participant demographics.

Running N Age (years) Height (m) Mass (kg) Experience (years)

RRMI 15 37.27±9.31 1.63±0.07 60.69±8.17 8.31±8.44

INJF 35 39.89±9.52 1.66±0.08 66.54±12.95 5.09±6.19

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Values are represented as – mean (standard deviation). No differences were present at baseline between the RRMI and INJF groups.

113

3.9 Figures

8.000

)

° 6.000 ( Mean Difference 1.64 ± 0.12° 4.000 Mean Difference INJF 1.44 ± 0.08° Pelvic Lift Pelvic 2.000 Mean Upper Limit 0.000 Lower Limit -2.000

RRMI

) Mean ° -4.000 Upper Limit -6.000 Lower Limit

Pelvic Drop ( Drop Pelvic -8.000

-10.000

1 6

36 56 11 16 21 26 31 41 46 51 61 66 71 76 81 86 91 96 101 % Stance Phase

Figure 3-1. Frontal plane pelvic kinematics during the stance phase of running. Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Mean values for the RRMI group (solid black line) and INJF group (solid gray line), with 90% confidence intervals (dotted lines). The stance phase of running is represented as 100 time points.

114

5.000

) 4.000

° ( 3.000

2.000 INJF Mean

1.000 Upper Limit Ipsilateral Lean Lean Ipsilateral

0.000 Lower Limit

) °

( -1.000 RRMI Mean -2.000 Upper Limit -3.000 Lower Limit -4.000 Mean Difference 1.19 ± 0.07°

Contralateral Lean Lean Contralateral -5.000

1 6

76 11 16 21 26 31 36 41 46 51 56 61 66 71 81 86 91 96 101 % Stance Phase

Figure 3-2. Frontal plane trunk kinematics during the stance phase of running. Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Mean values for the RRMI group (solid black line) and INJF group (solid gray line), with 90% confidence intervals (dotted lines). The stance phase of running is represented as 100 time points.

115

15.000

13.000

11.000

9.000

INJF Mean

) °

( 7.000 Upper Limit Lower Limit 5.000 RRMI Mean 3.000

Adduction Upper Limit

Lower Limit

) 1.000

° (

-1.000

-3.000

1 6

Abduction

11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101 % Stance Phase Figure 3-3. Frontal plane hip kinematics during the stance phase of running. Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Mean values for the RRMI group (solid black line) and INJF group (solid gray line), with 90% confidence intervals (dotted lines). The stance phase of running is represented as 100 time points.

116

0.000

-2.000

) -4.000

° ( INJF Mean -6.000 Upper Limit

-8.000 Lower Limit RRMI Mean

External Rotation Rotation External -10.000 Upper Limit Lower Limit -12.000

-14.000

1 6

16 86 11 21 26 31 36 41 46 51 56 61 66 71 76 81 91 96 101 % Stance Phase

Figure 3-4. Transverse plane hip kinematics during the stance phase of running. Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Mean values for the RRMI group (solid black line) and INJF group (solid gray line), with 90% confidence intervals (dotted lines). The stance phase of running is represented as 100 time points.

117

Chapter 4

Hip Strength and Trunk Endurance in Injured and Injury Free Runners Participating in a “Marathon in Training” Program: A Prospective Cohort Study

4.1 Abstract

Background: Hip muscle weakness is proposed to contribute to a variety of running related musculoskeletal injuries (RRMIs). Additionally, testing core musculature other than the hip muscles, such as the trunk flexors, extensors, and lateral flexors could identify muscles contributing to the global core instability seen at the hip, pelvis and trunk during running. However, only retrospective studies have been utilized to investigate the hip and core muscle strength and endurance, respectively. Objectives: To determine differences in isometric hip strength and trunk endurance baseline performance between female runners who sustain a RRMI during a “marathon in training” program and runners who remain injury-free. Study Design: Prospective cohort. Methods: Fifty female runners were recruited. Isometric hip abduction, external rotation, extension, and flexion strength, along with trunk flexion, extension, and lateral flexion endurance were tested prior to the start of the “marathon in training” program. RRMIs were tracked over

16 weeks, allowing for group allocation at the end of the training program. Results: 118

Fifteen females sustained a RRMI during training. There were no differences for all baseline strength and endurance variables between the female runners who sustained a

RRMI during training and the female runners that remained injury-free (P≥0.05).

However, the RRMI group did perform more curl-ups compared to the injury-free group, although not significant (P=0.074). Conclusion: Differences at a baseline testing session in isometric hip strength and trunk endurance do not exist between female runners who go on to sustain an RRMI during training and runners who remain injury free. Deficits in hip muscle strength seen in cross-sectional studies may be the result of a RRMI rather than a contributing factor. Future investigation into isolated core muscle strength and neuromuscular control is justified.

Keywords: hip strength, trunk endurance, running related musculoskeletal injury

4.2 Introduction

The etiology of running related musculoskeletal injuries (RRMI) is multifactorial in nature. Over the past decade, researchers have pursued an investigation into a link between the proximal hip joint and the presence of RRMIs distally. Patellofemoral pain

(PFP),(Dierks & Davis, 2008) iliotibial band syndrome (ITBS),(Ferber, Noehren, Hamill,

& Davis, 2010; Fredericson et al., 2000) tibial stress fractures (TSFX),(Milner, Hamill, &

Davis, 2010; Pohl, Mullineaux, Milner, Hamill, & Davis, 2008) and medial tibial stress syndrome (MTSS)(Loudon & Reiman, 2012) are just a few of the most prevalent RRMIs that have been linked to anomalies at the hip joint. According to the kinetic chain concept, alterations at one joint such as the hip, can manifest in compensations and injuries at other joints, both distally in the lower limb, and superiorly in the trunk.

119

When a runner presents to a clinic with an RRMI, hip strength is one of the mostly frequently assessed variables during the orthopedic evaluation. Using a hand-held dynamometer (HHD) to evaluate isometric strength is an efficient, inexpensive and reliable clinical tool, that can capture quantitative strength values.(Thorborg, Petersen,

Magnusson, & Holmich, 2010) Although there are a limited number of studies investigating hip strength in runners, isometric strength deficits of the hip abductors,(Dierks & Davis, 2008; Fredericson et al., 2000) and external rotators

(Noehren, Schmitz, Hempel, Westlake, & Black, 2014) have been observed in runners with an RRMI compared to injury free runners. With the presence of weak hip abductors and external rotators, running mechanics are believed to be altered contributing to increased hip adduction and internal rotation, and contralateral pelvic drop during the stance phase of running. However, the majority of studies investigating hip strength are retrospective in design, allowing no conclusion to be derived between sustaining a RRMI and the timing of hip strength deficits. Few studies to date have reported prospectively in runners the involvement of strength with the development of PFP.(Thijs, Pattyn, Van

Tiggelen, Rombaut, & Witvrouw, 2011) Thijs and colleagues tested isometric hip strength in all runners at baseline and then tracked the incidence of PFP over ten weeks.

For all hip strength measurements, flexion, extension, abduction, adduction, external and internal rotation, there were no differences between female runners who developed PFP and remained injury free. The authors propose that PFP might be the result of, rather than a predisposing factor for PFP. The role of the hip muscle strength in many RRMI populations has only been investigated retrospectively, thereby warranting a prospective examination of hip strength within a collective group of runners that may sustain a

120 variety of chronic injuries. Additionally, when examining male and female cross country and track and field athletes prospectively, those that sustained PFP had decreased hip abduction and external rotation strength compared to the pre-injury measurements.(Finnoff et al., 2011) These findings suggest that strength deficits of the hip abductors and external rotators could be the result of the injury as deficits were not found prior to developing PFP.

In accordance with the kinetic chain model, if a runner presents with proximal hip joint dysfunction, injuries can develop distally; however, additional compensations superior to the hips and at the trunk need also to be considered. When examining runners with PFP compared to healthy runners, researchers found increased hip adduction and internal rotation angles, as well as a trend towards increased ipsilateral trunk lean

(p=0.071).(Noehren, Pohl, Sanchez, Cunningham, & Lattermann, 2012) Global core instability, as evidence by increased hip, and pelvic movement during running could force the runner to lean towards the injured stance limb as a mechanism to reduce displacement of the body’s center of mass, and decrease the demands on the core musculature. Only one study has investigated core muscular strength in a RRMI population, that of participants with PFP.(Cowan, Crossley, & Bennell, 2009) Using the trunk side flexion test, the investigators found decreased strength of the lateral flexors in the injured group compared to a healthy control group. Although the participants were not runners, and consisted of both males and females, further investigation into the role of core muscular endurance is warranted. Running is an endurance sport, in which muscles are used repetitively over an extended period of time. In addition, testing the hip is only one component of the core complex. Thus, testing the lateral trunk flexors as well as

121 trunk flexors and extenders, could provide insight into mechanisms at the core related to the development of an RRMI.

Understanding the prospective role of hip strength and core endurance in females who sustain a RRMI could help facilitate pre-participation evaluations of runners.

Additionally, the identification of clinically modifiable predisposing factors such as hip strength and core endurance would allow clinicians to develop prevention programs aimed at keeping runners physically active and RRMI free. Therefore, the purpose of this study was to measure isometric hip abduction, external rotation, extension, and flexion strength, and trunk flexion, extension, and lateral flexion endurance in females runners participating in a “marathon in training” program. Additionally, we sought to identify differences amongst the variables between the runners who sustained a RRMI and remained injury free during training. Based on previously reported data in a variety of

RRMI populations, we hypothesized that female runners who sustained an RRMI would have decreased hip strength and core endurance compared to the runners who remained injury free.

4.3 Methods

4.3.1 Study Design

This population in the present study was the same as that in a previous prospective study.(Beard, Bazett-Jones, Donovan, Thomas, & Gribble, 2015) A single group of female runners were tested at baseline and tracked over a 16 week “marathon in training” program. Our independent variable was group (RRMI and injury free [INJF]), which was determined at the end of the program. The dependent variables were isometric 122 hip strength (abduction, external rotation, extension and flexion), and trunk endurance

(flexion, extension and lateral flexion).

4.3.2 Participants

The cohort of female runners is a subset of participants all who were enrolled in a

“marathon in training” program organized by a local running store. Participants were recruited via public announcements through the local running store. Female runners were excluded from this study if they had a previous RRMI or other non-RRMI injury of the lower extremity or back within the past 6 months, or were currently pregnant or breastfeeding. Prior to participation in the study, all individuals provided written informed consent (Appendix A). The study protocol was approved by the institution’s review board.

4.3.3 Instrumentation

Hip strength was assessed using a microFET2 (Hoggan Healthy Industries, Salt

Lake City, IT) handheld dynamometer (HHD). Hip strength was reported in Newton’s.

The HHD is a convenient and inexpensive clinical tool, which accurately assesses hip strength when compared to an isokinetic dynamometer. Additionally, when utilized across multiple testing sessions and by several clinicians, it has been shown to be highly reliable.(Thorborg et al., 2010) Trunk endurance was assessed using a general stop watch.

123

4.3.4 Procedures

Female runners recruited from the “marathon in training” program attended a baseline testing session prior to the start of the program, followed by the completion of questionnaires asking information pertaining to their injury and running history

(Appendices B-F). Participants were then positioned supine on a treatment table to allow the lead investigator to measure moment arm lengths.(Bazett-Jones, Cobb, Joshi, Cashin,

& Earl, 2011) Moment arm measurements were recorded to convert strength to torque values. For hip extension and flexion, the moment arm was measured from the greater trochanter of the femur to the lateral knee joint line. The moment arm for hip external rotation was measured from the base of the medial malleolus of the tibia to the medial knee joint line, while the moment arm for hip abduction was measured from the greater trochanter of the femur to the base of the lateral malleolus of the fibula. For all moment arms, 5.08 cm was subtracted, to represent the moment arm length from the joint axis to the placement of the HHD.

Participants completed a 5 minute warm-up prior to the initiation of hip strength testing. Hip strength tests were performed prior to the trunk endurance tests as the trunk endurance tests were deemed more fatiguing compared to the strength tests. The order of testing within the strength and endurance blocks was randomized, and all tests were performed bilaterally when applicable. The starting limb was randomized for all participants and kept consistent between tests.

For all hip strength tests, participants were instructed in the proper procedures, and performed one submaximal practice trial to become familiar with the test. The practice trial was followed by 3 recorded trials, consisting of a ramp up into a 5 second 124 maximal voluntary isometric contraction.(Kelln, McKeon, Gontkof, & Hertel, 2008)

Thirty seconds of rest was given between trials, while two minutes of rest was given between tests.(Stratford & Balsor, 1994) Verbal encouragement was provided by an examiner during the test, while another monitored for compensatory movements. If compensatory movements were seen, the participant was reminded of the correct technique, and the trial was repeated.

The testing positions for all hip strength tests were similar to ones utilized in previous research.(Thorborg et al., 2010) Hip abduction (HABD) strength was assessed in the supine position, with a stabilization belt over the participant’s anterior superior iliac spine (ASIS) to secure the participant to the table (Figure 4-1). The testing leg was in neutral. The HHD was placed at a mark 5.08cm proximal to the base of the lateral malleolus. For hip external rotation (HEXR) strength the participant was in the prone position with the stabilization belt secure over the posterior superior iliac spine (PSIS;

Figure 4-2). The knee of the testing limb was in 90 degrees of flexion, and the HHD was placed 5.08cm proximal to the medial malleolus. To test hip extension (HEXT) strength, the participant was in the prone position with the stabilization belt over the PSIS (Figure

4-3). The knee of the testing limb was flexed to 90 degrees, and the HHD was placed

5.08 cm proximal to the lateral femoral condyle on the posterior thigh. Hip flexion

(HFLX) strength was assessed in the supine position. The stabilization belt secured over the ASIS and the hip was flexed to 90 degrees (Figure 4-4). The HHD was placed 5.08 cm proximal to the lateral femoral condyle on the anterior thigh.

The trunk flexor (TFLX) endurance test was a modified version of that utilized by

Kahle and Tevald.(Kahle & Tevald, 2014) Participants began in the supine position, with

125 knees flexed and feet flat on the ground (Figure 4-5). The participant’s arms were at the sides of her body with palms flat on the ground, and a ruler was placed at her fingertips.

The participant was instructed to curl up using her abdominal muscles, while sliding the fingers on the floor. Once the participant’s fingers had moved 10cm, she then folded her arms across her chest while an investigator lowered a bar on to her arm. The bar represented the standardized height to which the participant had to curl-up to during each repetition. Curl ups were performed to the beat of a metronome at a rate of 30 curl ups per minute. One investigator stabilized the feet during testing and provided verbal encouragement, while another stabilized the bar and counted successful repetitions. The participant’s feet were restrained during testing, as a feet restrained curl up activates the abdominal muscles more compared to an unrestrained curl up.(Burden & Redmond,

2013) The participant performed as many repetitions until she: 1) failed to touch the bar,

2) fell off pace with the beat of the metronome for a total of three unsuccessful trials, or

3) became too fatigued to continue.

Posterior trunk extensor endurance (TEXT) was similar to the test conducted by

McGill et al., though with slight modification.(McGill, Childs, & Liebenson, 1999) Prior to the test, the participant was instructed on the proper procedure and a demonstration of the test by an investigator was performed. The participant was positioned prone with the lower extremity on a platform, aligned with the ASIS at the edge of the platform, and legs secured by an investigator at the calves (Figure 4-6). The upper extremity laid extended over the edge of the platform, with the participant resting her upper body on the floor until the beginning of the test. When ready, the participant exerted her trunk extensors, raising her upper body off of the floor, crossing her arms and resting her hands on the

126 opposite shoulders. The participant was instructed to maintain a horizontal position for as long as she could. Meanwhile, the investigators monitored for compensatory movements.

Verbal encouragement and instructions to correct posture were given. The test was terminated when either the participant received three separate instructions to correct posture, or when the participant’s upper body came in contact with the floor. The endurance test was recorded in seconds using a stop watch. The lateral trunk flexor tests

(LTFLX) were performed similarly to the posterior trunk endurance test, with the participant positioned on her side and the iliac crest at the edge of the platform (Figure 4-

7). A minimum of three minutes rest was given between trunk endurance tests.

4.3.5 “Marathon in Training” Program

The formalized “marathon in training” program was 16 weeks in length, and prepared participants for either a half or full marathon at the conclusion of the program.

4.3.6 Injury Tracking

Throughout the 16 week program, participants reported any RRMIs to the lead investigator. If injured, a participant had the option to see her own physician or physical therapist, or to see the physical therapist involved in this study. If the participant saw care

127 from her own healthcare practitioner, an injury form was completed by the clinician and returned to the lead investigator (Appendix G). If the participant sought care from the physical therapist involved in the present study, he filled out the form and returned it to the lead investigator. The injury form extracted information from the participant including location or injury, date of injury, description of pain, pain during various activities graded on a 100 point visual analog scale, treatment to date, and alterations to training program if any. The physician or physical therapist performed an evaluation and documented a diagnosis.

The definition of an RRMI utilized in this prospective cohort study was any chronic running related, musculoskeletal injury of the lower extremity or back that resulted in the participant seeking out a clinician and prompted one of the following: 1) modified or halted their running participation for at least one planned training day, including deviations in speed, time, or distance; or 2) performed an alternate, less demanding activity in replace of running for at least one planned, training day, including but not limited to biking, swimming or working out on an elliptical trainer.

4.3.7 Data Processing

Individual strength trials were reported in forces (Newton’s), and the three trials were averaged. The mean forces were multiplied by the appropriate moment arm length

(meters), and divided by the participant’s body mass (kilograms). Hence, strength measurements were reported as normalized values (Nm/kg) to allow for comparison across participants.

128

4.3.8 Statistical Analysis

For all statistical analyses the independent variable was group (RRMI and injury free [INJF]). For all comparisons, the injured limb of the RRMI group was compared with the average of the limbs of the INJF group. The dependent variables of interest were

HABD, HEXR, HEXT, and HFLX strength, and TFLX, TEXT, and LTFLX endurance.

Independent t-tests were used to assess group differences for each dependent variable

(SPSS version 21.0, SPSS Inc., Chicago, IL). Alpha was set a-prior as p≤0.05. In addition, Cohen’s d effect sizes were calculated in Microsoft Excel, along with 95% confidence intervals (95% CI).

4.4 Results

(n=1). Additionally, three runners sustained acute ankle sprains and were removed from analysis as the present study was interested in chronic RRMIs.

4.4.1 Running Related Musculoskeletal Injuries

Fifteen female runners sustained an RRMI during the “marathon in training” program, leaving 35 female runners injury-free at the conclusion of the program. Group demographics are reported in Table 4.1. There were no significant differences between groups for age, height, mass or running experience.

129

4.4.2 Hip Strength and Core Endurance

There were no significant differences for all isometric hip strength tests between the RRMI and INJF group. In addition, between groups there were no significant differences for all trunk endurance tests. However, there was a trend towards significance for the anterior trunk flexor endurance test. Compared to the INJF group, the RRMI groups demonstrated an increase in trunk flexor endurance at baseline, although not statistically significant (Table 4.2).

4.5 Discussion

Retrospective studies have examined hip strength deficits in a variety of runners, comparing injured runners with injury free runners. A limitation of a retrospective study is the inability to determine of hip strength abnormalities contributed to an RRMI, or are the result of the RRMI. Therefore, the purpose of this prospective study was to identify if hip strength and trunk endurance are predisposing factors for an RRMI in female runners participating in a “marathon in training” program. The result of the present study rejects our hypothesis and indicates that no strength deficits were present at baseline in the female runners who sustained an RRMI during training.

The results of the present study oppose those of studies investigating hip strength in injured and injury free runners using a retrospective case control design. Authors reporting on hip strength have utilized different methods of calculating strength, thus drawing comparison across studies is challenging; however, comparison between calculated effect sizes (Cohen’s d) is feasible as it represents the standardized difference between the group means. For hip abduction strength, the between group effect size value 130 was d=-0.24 for the present study, indicating low impact of muscle strength on the difference between groups. In a study comparing males with and without ITBS, there were no differences in HABD strength with a closely related effect size of d=0.026.(Noehren et al., 2014) However, the runners in the other study were males, not females as in the present study. Only one study to date has investigated whether or not isometric hip strength is a predisposing factor for injury in female runners, specifically for PFP. The researchers reported no differences for all six isometric hip strength measurements between runners who developed PFP compared to the asymptomatic runners.(Thijs et al., 2011) In the previous study, the magnitude of the effect was small for all strength variables (d= -0.17 to 0.28), similar to those in this study (d=-0.25 to

0.18). The results of the present study and Thijs et al support the notion that hip strength weaknesses may more likely be the result of an injury, rather than a predisposing factor.

It is extremely important to note that this does not negate the need for clinicians to examine hip strength in an injured runner. Strength deficits still need to be treated to minimize the duration of symptoms and should be done in conjunction with gait retraining and neuromuscular re-education. Conversely, when authors investigated eccentric rather than isometric hip strength and the influence on the development of PFP in novice runners, it was reported that increased eccentric hip strength reduced the risk for developing PFP, up to the first 50km of a self-structured training program.(Ramskov,

Barton, Nielsen, & Rasmussen, 2015) The authors chose hip eccentric strength as it mimicked the stance phase of running, in that the gluteus medius and maximus eccentrically control the hip and pelvis motion during this phase. However, due to the program being self-structured, it is hard to rule out other confounding factors such as

131 drastic changes in training pace, distance and frequency. In addition, the study included both male and female novice runners.

The lack of differences in trunk endurance between the RRMI and INJF group indicates that core muscular instability is more likely the result of the injury, rather than a contributing factor. Core muscular instability could be the result of an injury in the lower extremity causing compensatory running mechanics proximally. However, it is important to note that there was a moderate effect size for the trunk flexor endurance test between groups (d=0.64), indicating that the difference in group means may be due to trunk flexor endurance. However, the difference is conflicting of the proposed hypothesis, in that females with an RRMI performed better on the repetitive curl up test compared to healthy runners. Increased activation of the primary trunk flexors, such as the rectus abdominis and oblique muscles could be a compensatory mechanism to attempt to stabilize the pelvis. The anterior core musculature provides stability and coordinated movement within the lumbo-pelvic-hip complex. Runners who have an increased trunk lean during running exhibit lower energy absorption and generation by the knee extensors, and higher energy generation of the hip extensors decreasing the load on the knee joint.(Teng &

Powers, 2015) A forward trunk lean has been seen in other pathological populations including individuals with knee osteoarthritis or anterior cruciate ligament deficiencies during stair ascent and hop landing tasks who could be leaning forward at the trunk as compensatory strategy after injury to minimize joint loading on the knee joint.(Asay,

Mundermann, & Andriacchi, 2009; Oberlander, Bruggemann, Hoher, & Karamanidis,

2012) Trunk flexor and extensor endurance has yet to be examined in runners with

132

RRMIs and healthy runners using case control studies, thus it has yet to be determined if differences exist as the result of the injury.

Lateral trunk flexor strength has been investigated in individuals with PFP using the trunk side flexion test described by McGill et al.(Cowan et al., 2009) For the present study, a modified version of the trunk extensor test was utilized, with the participant in a sidelying position to test the lateral trunk flexors. The trunk side flexion test was not utilized due to pilot testing within runners, which found that 76% of our participants fatigued in the shoulder during the test. This same finding has been previously established; participants have reported shoulder pain that limited their holding time.(Greene, Durall, & Kernozek, 2011) As a limitation, the reliability of the suspended side trunk extensor test was not evaluated prior to the start of the present study.

A limitation of the present study was the use of multiple clinicians to test isometric hip strength. However, moderate to strong intertester reliability (ICC=0.65 to

0.87) and intratester reliability (ICC=0.77 to 0.97) has been documented suggesting the use of multiple testers is feasible, although not typically recommended.(Kelln et al.,

2008) Additionally, all efforts during the study were made to ensure consistency between clinicians, such as standardized placement of the HHD, consistent counting technique, and similar size of the testers. Additionally, the present study only examined one hip strength variable. Future research should investigate multiple hip strength measurements including concentric and eccentric, as well as the position in which the participants were positioned. The supine and prone positions utilized to test hip strength would not be considered functional, compared to the act of running. Research examining hip strength in the standing position, and utilizing eccentric testing could be more indicative of

133 running related strength. Lastly, testing maximum isometric voluntary contractions does not provide information such as the onset of muscle activity obtained via electromyography. Muscles pre-activate to prepare for the increased loading that occurs during the stance phase of running, perhaps contributing to the development of a RRMI.

4.6 Conclusion

Findings from this study provide support that isometric hip strength and trunk endurance are not predisposing factors for the development of a RRMI amongst female runners during training. Considering this, future research should investigate the role of eccentric hip strength, as well as neuromuscular control of the muscle such as activation onset time. Perhaps the eccentric control of the hip and pelvis during running, and how the muscle prepares for joint loading will be different between runners who sustain and

RRMI and those that remain injury free.

134

4.7 References

Asay, J. L., Mundermann, A., & Andriacchi, T. P. (2009). Adaptive patterns of

movement during stair climbing in patients with knee osteoarthritis. J Orthop Res,

27(3), 325-329.

Bazett-Jones, D. M., Cobb, S. C., Joshi, M. N., Cashin, S. E., & Earl, J. E. (2011).

Normalizing hip muscle strength: establishing body-size-independent

measurements. Arch Phys Med Rehabil, 92(1), 76-82.

Beard, M., Bazett-Jones, D., Donovan, L., Thomas, A., & Gribble, P. (2015). Running

biomechanics in injured and injury free runners participating in a "marathon in

training" program: a prospective cohort study. University of Toledo.

Burden, A. M., & Redmond, C. G. (2013). Abdominal and hip flexor muscle activity

during 2 minutes of sit-ups and curl-ups. J Strength Cond Res, 27(8), 2119-2128.

Cowan, S. M., Crossley, K. M., & Bennell, K. L. (2009). Altered hip and trunk muscle

function in individuals with patellofemoral pain. Br J Sports Med, 43(8), 584-588.

Dierks, T. A., & Davis, I. (2008). Lower extremity alignment and knee valgus during

prolonged running in runners with patellofemoral pain. Med Sci Sports Exerc,

40(5), S339-S340.

Ferber, R., Noehren, B., Hamill, J., & Davis, I. (2010). Competitive female runners with

a history of iliotibial band syndrome demonstrate atypical hip and knee

kinematics. J Orthop Sports Phys Ther, 40(2), 52-58.

Finnoff, J. T., Hall, M. M., Kyle, K., Krause, D. A., Lai, J., & Smith, J. (2011). Hip

strength and knee pain in high school runners: a prospective study. PM&R, 3(9),

792-801. 135

Fredericson, M., Cookingham, C. L., Chaudhari, A. M., Dowdell, B. C., Oestreicher, N.,

& Sahrmann, S. A. (2000). Hip abductor weakness in distance runners with

iliotibial band syndrome. Clin J Sport Med, 10(3), 169-175.

Greene, P. F., Durall, C. J., & Kernozek, T. W. (2011). Intersession reliability and

concurrent validity of isometric endurance tests for the lateral trunk muscles. J

Sport Rehabil(21), 161-166.

Kahle, N., & Tevald, M. A. (2014). Core muscle strengthening’s improvement of balance

performance in community-dwelling older adults: a pilot study. J Aging Phys Act,

22, 65-73.

Kelln, B. M., McKeon, P. O., Gontkof, L. M., & Hertel, J. (2008). Hand-held

dynamometry: reliability of lower extremity muscle testing in healthy, physically

active,young adults. J Sport Rehabil, 17(2), 160-170.

Loudon, J. K., & Reiman, M. P. (2012). Lower extremity kinematics in running athletes

with and without a history of medial shin pain. Int J Sports Phys Ther, 7(4), 356-

364.

McGill, S. M., Childs, A., & Liebenson, C. (1999). Endurance times for low back

stabilization exercises: Clinical targets for testing and training from a normal

database. Arch Phys Med Rehabil, 80(8), 941-944.

Milner, C. E., Hamill, J., & Davis, I. S. (2010). Distinct hip and rearfoot kinematics in

female runners with a history of tibial stress fracture. J Orthop Sports Phys Ther,

40(2), 59-66.

136

Noehren, Pohl, M. B., Sanchez, Z., Cunningham, T., & Lattermann, C. (2012). Proximal

and distal kinematics in female runners with patellofemoral pain. Clin Biomech,

27(4), 366-371.

Noehren, Schmitz, A., Hempel, R., Westlake, C., & Black, W. (2014). Assessment of

strength, flexibility, and running mechanics in men with iliotibial band syndrome.

J Orthop Sport Phys, 44(3), 217-222.

Oberlander, K. D., Bruggemann, G. P., Hoher, J., & Karamanidis, K. (2012). Reduced

knee joint moment in ACL deficient patients at a cost of dynamic stability during

landing. J Biomech, 45(8), 1387-1392.

Pohl, M. B., Mullineaux, D. R., Milner, C. E., Hamill, J., & Davis, I. S. (2008).

Biomechanical predictors of retrospective tibial stress fractures in runners. J

Biomech, 41(6), 1160-1165.

Ramskov, D., Barton, C., Nielsen, R. O., & Rasmussen, S. (2015). High eccentric hip

abduction strength reduces the risk of developing patellofemoral pain among

novice runners initiating a self-structured running program: a 1-year observational

study. J Orthop Sports Phys Ther, 45(3), 153-161.

Stratford, P. W., & Balsor, B. E. (1994). A comparison of make and break tests using a

hand-held dynamometer and the Kin-Com. J Orthop Sports Phys Ther, 19(1), 28-

32.

Teng, H. L., & Powers, C. M. (2015). Influence of trunk posture on lower extremity

energetics during running. Med Sci Sports Exerc, 47(3), 625-630.

137

Thijs, Y., Pattyn, E., Van Tiggelen, D., Rombaut, L., & Witvrouw, E. (2011). Is hip

muscle weakness a predisposing factor for patellofemoral pain in female novice

runners? A prospective study. Am J Sports Med, 39(9), 1877-1882.

Thorborg, K., Petersen, J., Magnusson, S. P., & Holmich, P. (2010). Clinical assessment

of hip strength using a hand-held dynamometer is reliable. Scand J Med Sci

Sports, 20(3), 493-501.

138

4.8 Tables

Table 4.1. Participant demographics.

N Age (years) Height (m) Mass (kg)

RRMI 15 37.27±9.30 1.63±0.07 60.69±8.17

INJF 35 39.89±9.52 1.66±0.08 66.54±12.95

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Values are represented as – mean (standard deviation) No differences were present at baseline between the RRMI and INJF groups.

139

Table 4.2. Group comparisons between runners with a running related musculoskeletal injury and injury free runners for isometric hip strength*

Cohen’s d RRMI INJF P Value 95% CI Effect Size

HABD 1.13±0.32 1.19±0.25 0.550 -0.24 -0.85 to 0.37

HEXR 0.47±0.07 0.49±0.08 0.392 -0.25 -0.86 to 0.36

HEXT 0.71±0.14 0.70±0.20 0.741 0.05 -0.55 to 0.65

HFLX 0.79±0.14 0.76±0.17 0.494 0.18 -0.43 to 0.78

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free; HABD, hip abduction; HEXR, hip external rotation; HEXT, hip extension; HFLX, hip flexion; CI, confidence interval. *Hip strength (N) was multiplied by the moment arm (m) and normalized to boy mass (kg). Values are mean ± standard deviation.

140

Table 4.3. Group comparisons between runners with a running related musculoskeletal injury and injury free runners for trunk endurance*

Cohen’s d RRMI INJF P Value 95% CI Effect Size

TFLX 34.73±17.06 27.02±12.04 0.074 0.64 0.02 to 1.26

TEXT 188.88±59.16 165.12±71.11 0.262 0.33 -0.27 to 0.94

LTFLX 68.38±25.99 63.62±25.83 0.554 0.18 -0.42 to 0.79

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free; TFLX, trunk flexion; TEXT, trunk extension; LTFLX, lateral trunk flexion; CI, confidence interval. *TFLX is reported in repetitions; TEXT and LTFLX are reported in seconds. Values are mean ± standard deviation.

141

4.9 Figures

Figure 4-1. Hip abduction strength test.

Figure 4-2. Hip external rotation strength test.

142

Figure 4-3. Hip extension strength test.

Figure 4-4. Hip flexion strength test.

143

Figure 4-5. Trunk flexor endurance test. A) Starting position.

B) Finish position.

144

Figure 4-6. Trunk extensor endurance test.

Figure 4-7. Lateral trunk flexor endurance test.

145

Chapter 5

Relationship between Hip Strength, Core Endurance, and Trunk, Pelvic and Hip Kinematics during Running in Injured and Injury Free Runners

5.1 Abstract

Background: Altered running biomechanics and decreased hip strength have been identified in runners with running related musculoskeletal injuries (RRMIs) such as patellofemoral pain, and iliotibial band friction syndrome. Minimal research has examined the relationship between strength, endurance and running kinematics in both runners with a RRMI and injury free runners. Objectives: To determine the relationship of hip strength and core endurance, with frontal plane running kinematics at the trunk, pelvis, and hip in both injured and injury free (INJF) runners. Study Design: Prospective

Cohort. Methods: Data from fifty female runners were analyzed (RRMI n=15, INJF n=35). A three dimensional analysis of running biomechanics was performed, followed by isometric hip external rotation, abduction, extension, and flexion strength testing, and anterior, posterior, and lateral trunk flexor endurance testing. Results: Contralateral pelvic drop was positively correlated with isometric hip abduction strength and trunk extension endurance. Additionally, ipsilateral trunk lean was negatively correlated with 146 lateral trunk flexion endurance. There were no correlations between peak hip adduction during running and the strength and endurance variables. Conclusion: Decreased contralateral pelvic drop during running is partially controlled by the trunk extensors and hip abductors. Additionally, an increase in ipsilateral trunk lean during running has a negative correlation to decreased lateral trunk flexion strength. These results suggest the assessment of both the hip and trunk in the evaluation and treatment of RRMIs.

Keywords: running kinematics, hip strength, trunk endurance, running related musculoskeletal injury.

5.2 Introduction

Running is the most popular physical activity amongst Americans, as it is inexpensive, time efficient, and provides substantial healthy benefits.(USA, 2013)

However for many, the positive health benefits are overshadowed by running related musculoskeletal injuries (RRMI). The incidence of RRMIs has been reported as high as

80% amongst a plethora of running populations.(van Gent et al., 2007) Although RRMI rates are substantial, the etiology of RRMIs still remains not well understood. Many factors contribute to the development of RRMIs, ranging from training related factors to health factors; yet for almost all of these variables there remains conflicting evidence of their contribution to RRMI development.(van Gent et al., 2007) The investigation into biomechanical factors influencing RRMIs has been limited to factors such as arch index(Wen, Puffer, & Schmalzried, 1998) and subtalar positioning.(Lun, Meeuwisse,

Stergiou, & Stefanyshyn, 2004) These measurements of biomechanical lower limb static

147 alignment have been identified to not be related to development of a lower extremity

RRMI.

Other biomechanical factors such as muscular strength and running kinematics have been investigated within runners with specific RRMIs such as patellofemoral pain

(PFP), iliotibial band syndrome (ITBS), medial tibial stress syndrome (MTSS), and tibial stress fractures (TSF). Abnormal movement proximally at the hip, pelvis and trunk during running can result in abnormal mechanics distally. When anatomical structures distally attempt to compensate for musculoskeletal deficiencies proximally, the transfer of faulty mechanics and increased forces can overload structures resulting in an injury.(Loudon & Reiman, 2012) When dysfunction occurs throughout the lower extremity and trunk, and then stressed repetitively during the single limb stance of running, over time it can lead towards one of many chronic RRMIs.

When examining musculoskeletal dysfunction at the hip, an increase in hip adduction has been recognized in runners with RRMIs (Ferber, Noehren, Hamill, &

Davis, 2010; Milner, Hamill, & Davis, 2010; Noehren, Pohl, Sanchez, Cunningham, &

Lattermann, 2012; B. Noehren, Davis, & Hamill, 2007; Pohl, Mullineaux, Milner,

Hamill, & Davis, 2008) as has weaknesses in the hip abductors.(Dierks & Davis, 2008;

Fredericson et al., 2000) Weakness of the hip abductors could lead to minimized control of the hip joint, resulting in increased hip adduction during running. In addition, hip abductors function to maintain a level pelvis during single limb support. Hence, a decrease in hip abductor strength could lead to an increase in contralateral pelvic drop during the stance phase of running. Runners with a variety of RRMIs have exhibited an

148 increased, or trend towards increased contralateral pelvic drop during the stance phase of running compared to injury free runners.(Loudon & Reiman, 2012; Noehren et al., 2012)

The hip abductors are not the only stabilizers of the lumbo-pelvic-hip complex; the trunk muscles including the erector spinae, lumbar multifidi, quadratus lumborum, and oblique muscles, as well as the gluteus maximus contribute to core stability.

Insufficiencies in any number of these muscles can result in instability. On the other hand, increased stress can be placed on these muscles resulting in increased activation when muscles such as the hip abductors are weak. A trend towards increased ipsilateral trunk lean has been observed in female runners with PFP.(Noehren et al., 2012)

Ipsilateral trunk flexion during running could be a compensatory mechanism to minimize stresses on weak or injured trunk stabilizers, and minimize accessory shifting of the center of mass and sway of the upper extremity. This is supported by the finding that individuals with PFP, although not runners, have presented with decreased lateral trunk flexion strength compared to healthy individuals.(Cowan, Crossley, & Bennell, 2009)

To our knowledge, within the RRMI literature the direct association between hip strength and trunk endurance, and frontal plane running kinematics of the trunk, pelvis, and hip have not yet been investigated. Therefore, the purpose of this investigation was to compare isometric hip strength and core endurance to three frontal plane kinematic variables during the stance phase of running: hip adduction, contralateral pelvic drop, and ipsilateral trunk lean. It was hypothesized that decreased hip abduction, external rotation, and extension strength, and decreased trunk flexion, trunk extension, and lateral trunk flexion endurance would be related to increased peak hip adduction, contralateral pelvic drop and ipsilateral trunk lean during the stance phase of running. If a relation is

149 identified between strength, endurance and running kinematics, clinicians and researchers can utilize this information to guide prevention and intervention programs for a variety of

RRMIs.

5.3 Methods

5.3.1 Study Design

The present study utilizes the same participants as reported in a previous prospective study.(Beard, Bazett-Jones, Donovan, Thomas, & Gribble, 2015b) This study however, is a cohort study investigating the association between running kinematics

(peak trunk, pelvis, and hip frontal plane angles) hip strength (abduction, external rotation, and extension), and trunk endurance (flexion, extension and lateral flexion).

5.3.2 Participants

The cohort of female runners is a subset of participants enrolled in a “marathon in training” program organized by a local running store. Participants were recruited via public announcements through the local running store. Females included in this study had varying degrees of running experience, participation in a GTP and history of running half or full marathons. Female runners were excluded from this study if they had a previous injury or RRMI of the lower extremity or back within the past 6 months, or were currently pregnant or breastfeeding. Prior to participation in the study, all individuals provided written informed consent (Appendix A). The study protocol was approved by the institution’s review board.

150

5.3.3 Instrumentation

Kinematic and kinetic data was collected using a 12 camera motion analysis system (Motion Analysis Corporation) operating at a sampling frequency of 200 Hz, and an AMTI force plate (Advanced Mechanical Technology Inc., Watertown, MA) operating at a sampling frequency of 1000Hz was synchronized with the motion capture system.

Hip strength was assessed using a microFET2 (Hoggan Healthy Industries, Salt

Lake City, IT) handheld dynamometer (HHD). Hip strength was reported in Newton’s.

The HHD is a convenient and inexpensive clinical tool that accurately assesses hip strength, compared to an isokinetic dynamometer. Additionally, when utilized across multiple testing sessions and clinicians, it has been shown to be highly reliable.(Thorborg, Petersen, Magnusson, & Holmich, 2010) Trunk endurance was assessed using a general stop watch.

5.3.4 Procedures

The following procedures are equivalent to those in other studies using the same population.(Beard, Bazett-Jones, Donovan, Thomas, & Gribble, 2015a; Beard et al.,

2015b) Upon arrival to the testing session, written informed consent from the participants was retrieved, followed by the completion of questionnaires asking information pertaining to their injury and running history. Participants were then positioned supine on a treatment table to allow the lead investigator to measure moment arm lengths for normalization of the strength data.(Bazett-Jones, Cobb, Joshi, Cashin, & Earl, 2011)

Moment arm measurements were recorded to convert strength to torque values. For hip 151 extension and flexion, the moment arm was measured from the greater trochanter of the femur to the lateral knee joint line. The moment arm for hip external rotation was measured from the base of the medial malleolus of the tibia to the medial knee joint line, while the moment arm for hip abduction was measured from the greater trochanter of the femur to the base of the lateral malleolus of the fibula. For all moment arms, 5.08 cm was subtracted, to represent the moment arm length from the joint axis to the placement of the

HHD.

Participants completed a 5 minute warm-up prior to the initiation of all testing.

All runners wore tight fitting clothing and were fitted with forty-one retroreflective markers placed on anatomical landmarks including bilateral acromion process, iliac crest, posterior superior iliac spine (PSIS), anterior superior iliac spine (ASIS), greater trochanter, lateral thigh, anterior-distal thigh, lateral and medial femoral condyles, tibial tuberosity, lateral shank, medial and lateral malleolus, heel, first and fifth metatarsal heads, navicular bone, and second toe, as well as the manubrium, seventh cervical spinous process, and right scapula. Participants stood in the lab coordinate space with feet shoulder width apart, facing the direction of the dynamic running trials. A static trial was collected for 3 seconds to allow for the creation of a 3D model for each participant during data processing. Following the static calibration trial, anatomical markers on the iliac crest, medial femoral condyles, medial malleoli, and first and fifth metatarsal heads were removed. The marker set was a modified version of that used previously.(Salsich &

Long-Rossi, 2010)

Participants were given as many practice trials as necessary to become familiar with their speed and environment while running over ground. Running trials were

152 performed along a 15 meter runway at a self-selected pace. A self-selected pace was utilized over a standard pace due to the highly varied paces of runners participating in this study. In addition, RRMIs more commonly occur during training at a self-selected pace, thus the self-selected pace mirrored the participant’s normal training habits.(Miller,

Lowry, Meardon, & Gillette, 2007) Running velocity was monitored using timing gaits

Hip strength tests were performed prior to the trunk endurance tests as the trunk endurance tests were deemed more fatiguing compared to the strength tests. The strength tests and endurance tests were randomized, and all tests were performed bilaterally when applicable. For all hip strength tests, participants were instructed in the proper procedures, and performed one submaximal practice trial to become familiar with the test. The practice trial was followed by 3 recorded trials, consisting of a ramp up into a 5 second maximal voluntary isometric contraction.(Kelln, McKeon, Gontkof, & Hertel,

153

2008) Thirty seconds of rest was given between trials, while two minutes of rest was given between tests.(Stratford & Balsor, 1994) Verbal encouragement was provided by an examiner during the test, while another monitored for compensatory movements during testing. If compensatory movements were seen, the participant was reminded of the correct technique, and the trial was repeated.

The testing positions for all hip strength tests were similar to ones utilized in previous research.(Thorborg et al., 2010) Hip abduction (HABD) strength was assessed in the supine position, with a stabilization belt over the participant’s anterior superior iliac spine (ASIS) to secure the participant to the table (Figure 5-1). The testing leg was in neutral. The HHD was placed at a mark 5.08cm proximal to the base of the lateral malleolus. For hip external rotation (HEXR) strength the participant was in the prone position with the stabilization belt secure over the posterior superior iliac spine (PSIS;

Figure 5-2). The knee of the testing limb was flexed to 90 degrees, and the HHD was placed 5.08cm proximal to the medial malleolus. To test hip extension (HEXT) strength, the participant was in the prone position with the stabilization belt over the PSIS (Figure

5-3). The knee of the testing limb was flexed to 90 degrees of flexion, and the HHD was placed 5.08 cm proximal to the lateral femoral condyle on the posterior thigh.

The trunk flexor (TFLX) endurance test was a modified version of that utilized by

Kahle and Tevald.(Kahle & Tevald, 2014) Participants began in the supine position, with knees flexed and feet flat on the ground (Figure 5-4). The participant’s arms were at the sides of the body with palms flat on the ground, and a ruler placed at the participants fingertips. The participant was instructed to curl up using her abdominal muscles, while sliding the fingers on the floor. Once the participant’s fingers had moved ten centimeters,

154 she then folded her arms across her chest, while an investigator lowered a bar on to the participant’s arm. The bar represented the standardized height to which the participant had to curl-up to during each repetition. Curl ups were performed to the beat of a metronome at a rate of 30 curl ups per minute. One investigator stabilized the feet during testing and provided verbal encouragement, while another stabilized the bar and counted successful repetitions. Feet were restrained during testing, as a feet restrained curl up activates the abdominal muscles more compared to an unrestrained curl up.(Burden &

Redmond, 2013) The participant performed as many repetitions as possible until the participant failed to touch the bar or fell off pace with the beat of the metronome for a total of three unsuccessful trials, or became too fatigued to continue.

Trunk extensor (TEXT) endurance was similar to the test conducted by McGill et al., though with slight modification.(McGill, Childs, & Liebenson, 1999) Prior to the test, the participant was instructed on the proper procedure and a demonstration of the test by an investigator was performed. The participant was positioned prone with the lower extremity on a platform, aligned with the ASIS at the edge of the platform, and legs secured by an investigator at the calves (Figure 5-5). The upper extremity laid extended over the edge of the platform, with the participant resting her upper body on the floor until the beginning of the test. When ready, the participant exerted her trunk extensors, raising the upper body off of the floor, crossing the arms and resting the hands on opposite shoulders. The participant was instructed to maintain a horizontal position for as long as she could. Meanwhile, the investigators monitored for compensatory movements.

Verbal encouragement and instructions to correct posture were given. The test was terminated when either the participant received three separate instructions to correct

155 posture, or when the participant’s upper body came in contact with the floor. The endurance test was recorded in seconds using a stop watch. The lateral trunk flexor

(LTFLX) endurance tests were performed similar to that as the posterior trunk endurance test, with the participant position on her side and the iliac crest at the edge of the platform

(Figure 5-6). A minimum of three minutes rest was given between trunk endurance tests.

The present study was a part of a larger prospective study in which all female runners were tested at baseline, prior to the initiation of a 16 week “marathon in training program”. Over the 16 weeks RRMIs were tracked by a certified athletic trainer and licensed physical therapist using a previously established injury definition. At the end of the program, 5 participants were removed from analysis, 15 female runners had sustained a RRMI, and 35 remained healthy. The data collected on these 50 females were included in the analysis.

5.3.5 Data Processing

Hip, pelvic and trunk kinematics, and ground reaction forces (GRF) for each running trial were calculated using Visual3D software (C-Motion Inc, Rockville, MD).

Kinematic and kinetic data were low-pass filtered at 12Hz and 50Hz, respectively, with a fourth-order zero lag Butterworth filter. The stance phase was determined using the vertical ground reaction force (vGRF). Foot strike and toe off we defined as the point in which the vGRF went above and below 20N respectfully. All running biomechanical data were normalized across the stance phase (100 data points) and averaged for each participant. Directions of joint movement were defined using the right hand rule. The kinematic variables of interest were peak ipsilateral trunk flexion, contralateral pelvic

156 drop and hip adduction during the stance phase of each running trial. Peak values were extracted from all viable trials and averaged.

Individual strength trials were reported in forces (Newton’s), and the three trials were averaged. The mean forces were multiplied by the appropriate moment arm length

(meters), and divided by the participant’s mass (kilograms). Hence strength measurements were reported as normalized values (Nm/kg) to allow for comparison across participants.

5.3.6 Statistical Analysis

Data were analyzed using SPSS (version 21.0, SPSS Inc., Chicago, IL). Alpha was set a-prior as p≤0.05. The data were initially assessed for outliers, which were defined as a value greater than three standard deviations away from the mean. Simple bivariate correlation analyses were utilized to establish the relationship between the strength and endurance variables, and running kinematics amongst all female runners.

5.4 Results

A total of fifty participants were reported in the previous studies, having an average age, height and mass of 39 years (standard deviation, SD ± 9), 1.65 meters (SD ±

0.07), and 64.78 kilograms (SD ± 11.95) respectfully. One outlier was identified within the following variables: HEXT, TFLX, TEXT, and LTFLX. The outlier value was replaced with the mean of the assigned group. Descriptive characteristics for both the

RRMI and INJF groups are presented in table 5.2.

157

There was a weak, association between peak contralateral pelvic drop during the stance phase of running and TEXT endurance (r=0.319, p=0.024) (Figure 5-7), as well as isometric hip abduction strength (r=0.297, p=0.036) (Figure 5-8). Additionally, there was a negative, weak correlation between peak ipsilateral trunk flexion during the stance phase of running and lateral trunk flexion endurance strength (r=-0.303, p=0.033) (Figure

5-9). There was no association between peak hip adduction during the stance phase of running and any of the strength or endurance variables (Table 5.3).

5.5 Discussion

The purpose of this study was to identify the relationship between frontal plane movement at the trunk, pelvis and hip during running, and strength and endurance of the hip and trunk muscles, respectively amongst female runners with and without an RRMI.

This investigation is novel, and provides both support for and against the relationship between running kinematics, strength, and endurance. The principal findings of the investigation are a weak correlation between peak contralateral pelvic drop during the stance phase of running and isometric hip abduction strength and trunk extension endurance, as well as between peak ipsilateral trunk flexion and lateral trunk flexion endurance.

During mid-stance phase of running, the hip will be in an adducted position relative to the pelvis, the contralateral pelvis will be slightly lower, and the trunk will be in ipsilateral trunk flexion.(Dicharry, 2010) Dicharry stated that too much movement within the lumbo-pelvic-hip complex during running could lead to an RRMI. Accessory hip adduction and contralateral pelvic drop could be the result of weak hip abductors.

158

Weak hip abduction has been identified in females with specific RRMIs such as

PFP(Dierks & Davis, 2008; Souza & Powers, 2009) and ITBS(Fredericson et al., 2000) as has a trend towards decreased contralateral pelvic drop in females with PFP.(Noehren et al., 2012) The present study is the first to examine the relation between frontal plane kinematics of the pelvis during running and hip strength. Future research should investigate the relation between neuromuscular activation timing and peak amplitude, and frontal plane pelvic kinematics. If there is a delay in activation of the pelvic stabilizers, they may not be prepared to properly stabilize the pelvis prior to impact and peak vertical ground reaction force leading to strain on the muscles, and decreased pelvic drop.

Core stability is provided by muscles both through motor control and the muscular capacity of the lumbo-pelvic-hip complex,(Leetun, Ireland, Willson,

Ballantyne, & Davis, 2004) suggesting that more than the hip muscles could be involved in abnormal mechanics of the pelvis. The finding of a weak correlation between peak contralateral pelvic drop and trunk extensor endurance provides evidence to support the role of the trunk extensors in the stabilization of the pelvis. However, muscles tested during the trunk extensor endurance test include the erector spinae, lumbar multifidi, quadratus lumborum, gluteus maximus, and hamstrings, amongst several others. The endurance test ends when the participant becomes fatigued within one of these muscles.

Unfortunately, it was not recorded where the participants fatigued, in the muscles of the posterior chain.

The third significant finding of the present study was a negative relation between ipsilateral trunk flexion and lateral trunk flexion endurance. Female runners, who presented with an increased ipsilateral trunk flexion during running, had decreased lateral

159 trunk flexion endurance. Decreased lateral trunk flexion strength using the side bridge test and a HHD has been identified in individuals with PFP.(Cowan et al., 2009) Direct comparison should be limited as the participant population in the previous study was not runners, the authors used isometric strength of the lateral trunk flexors, and no comparison was made to kinematics during dynamic movements. Runners however, may laterally flex the trunk towards the stance limb as a result of decreased core stability, thus placing less demand on the lateral trunk stabilizers. The present study choose to use a modified version of the trunk extensor test, as pilot testing amongst runners using the side bridge test yielded 76% of the participants to end the test due to fatigue in the shoulder not the lateral core.

Opposite of our hypothesis, this study did not find a relationship between isometric hip abduction strength and peak hip adduction angle during running. This is consistent with Dierks et al. who found no association between isometric hip abduction strength and hip adduction angle during the stance phase of running when in a non- fatigued state.(Dierks & Davis, 2008) However, the authors did report a significant relation between the variables once the injured runners reached a fatigued state. This relation was not evident in the non-injured runners in both a fatigued and non-fatigued state. Hence, testing hip abduction in a fatigued state could be more indicative of hip adduction angle during running, as the fatigued state could represent a threshold in which the muscles can no longer control hip movement, or stabilize the pelvis.

160

5.6 Conclusion

In conclusion, the present study adds to the growing RRMI literature supporting a potential connection between hip strength, core endurance, and running kinematics.

Although the relationship of contralateral pelvic drop during running to isometric hip abduction strength and trunk extension endurance was weak, it signifies that core stability is altered with an RRMI, and may play a role in the distal compensations that need further investigation. The assessment of runners with a RRMI should include running biomechanical analysis of the entire kinetic chain, as well as a global core strength and endurance assessment of the core and lower extremity muscle groups.

161

5.7 References

Bazett-Jones, D. M., Cobb, S. C., Joshi, M. N., Cashin, S. E., & Earl, J. E. (2011).

Normalizing hip muscle strength: establishing body-size-independent

measurements. Arch Phys Med Rehabil, 92(1), 76-82.

Beard, M., Bazett-Jones, D., Donovan, L., Thomas, A., & Gribble, P. (2015a). Hip

strength and trunk endurance in injured and injury free runners participating in a

"marathon in training" program: a prospective cohort study. University of

Toledo.

Beard, M., Bazett-Jones, D., Donovan, L., Thomas, A., & Gribble, P. (2015b). Running

biomechanics in injured and injury free runners participating in a "marathon in

training" program: a prospective cohort study. University of Toledo.

Burden, A. M., & Redmond, C. G. (2013). Abdominal and hip flexor muscle activity

during 2 minutes of sit-ups and curl-ups. J Strength Cond Res, 27(8), 2119-2128.

Cowan, S. M., Crossley, K. M., & Bennell, K. L. (2009). Altered hip and trunk muscle

function in individuals with patellofemoral pain. Br J Sports Med, 43(8), 584-588.

Dicharry, J. (2010). Kinematics and kinetics of gait: from lab to clinic. Clin Sport Med,

29(3), 347-364.

Dierks, T. A., & Davis, I. (2008). Lower extremity alignment and knee valgus during

prolonged running in runners with patellofemoral pain. Med Sci Sports Exerc,

40(5), S339-S340.

Ferber, R., Noehren, B., Hamill, J., & Davis, I. (2010). Competitive female runners with

a history of iliotibial band syndrome demonstrate atypical hip and knee

kinematics. J Orthop Sports Phys Ther, 40(2), 52-58. 162

Fredericson, M., Cookingham, C. L., Chaudhari, A. M., Dowdell, B. C., Oestreicher, N.,

& Sahrmann, S. A. (2000). Hip abductor weakness in distance runners with

iliotibial band syndrome. Clin J Sport Med, 10(3), 169-175.

Kahle, N., & Tevald, M. A. (2014). Core muscle strengthening’s improvement of balance

performance in community-dwelling older adults: a pilot study. J Aging Phys Act,

22, 65-73.

Kelln, B. M., McKeon, P. O., Gontkof, L. M., & Hertel, J. (2008). Hand-held

dynamometry: reliability of lower extremity muscle testing in healthy, physically

active,young adults. J Sport Rehabil, 17(2), 160-170.

Leetun, D. T., Ireland, M. L., Willson, J. D., Ballantyne, B. T., & Davis, I. (2004). Core

stability measures as risk factors for lower extremity injury in athletes. Med Sci

Sports Exerc, 36(6), 926-934.

Loudon, J. K., & Reiman, M. P. (2012). Lower extremity kinematics in running athletes

with and without a history of medial shin pain. Int J Sports Phys Ther, 7(4), 356-

364.

Lun, V., Meeuwisse, W., Stergiou, P., & Stefanyshyn, D. (2004). Relation between

running injury and static lower limb alignment in recreational runners. Br J Sports

Med, 38(5), 576-580.

McGill, S. M., Childs, A., & Liebenson, C. (1999). Endurance times for low back

stabilization exercises: Clinical targets for testing and training from a normal

database. Arch Phys Med Rehabil, 80(8), 941-944.

163

Miller, R. H., Lowry, J. L., Meardon, S. A., & Gillette, J. C. (2007). Lower extremity

mechanics of iliotibial band syndrome during an exhaustive run. Gait Posture,

26(3), 407-413.

Milner, C. E., Hamill, J., & Davis, I. S. (2010). Distinct hip and rearfoot kinematics in

female runners with a history of tibial stress fracture. J Orthop Sports Phys Ther,

40(2), 59-66.

Noehren, Pohl, M. B., Sanchez, Z., Cunningham, T., & Lattermann, C. (2012). Proximal

and distal kinematics in female runners with patellofemoral pain. Clin Biomech,

27(4), 366-371.

Noehren, B., Davis, I., & Hamill, J. (2007). Prospective study of the biomechanical

factors associated with iliotibial band syndrome. Clin Biomech, 22(9), 951-956.

Pohl, M. B., Mullineaux, D. R., Milner, C. E., Hamill, J., & Davis, I. S. (2008).

Biomechanical predictors of retrospective tibial stress fractures in runners. J

Biomech, 41(6), 1160-1165.

Salsich, G. B., & Long-Rossi, F. (2010). Do females with patellofemoral pain have

abnormal hip and knee kinematics during gait? Physiother Theory Pract, 26(3),

150-159.

Souza, R. B., & Powers, C. M. (2009). Differences in hip kinematics, muscle strength,

and muscle activation between subjects with and without patellofemoral pain. J

Orthop Sports Phys Ther, 39(1), 12-19.

Stratford, P. W., & Balsor, B. E. (1994). A comparison of make and break tests using a

hand-held dynamometer and the Kin-Com. J Orthop Sports Phys Ther, 19(1), 28-

32.

164

Thorborg, K., Petersen, J., Magnusson, S. P., & Holmich, P. (2010). Clinical assessment

of hip strength using a hand-held dynamometer is reliable. Scand J Med Sci

Sports, 20(3), 493-501.

USA, S. M. S. (2013). 2013 Participation Report (P. A. Council, Trans.) (2013 ed., pp.

15). van Gent, R. N., Siem, D., van Middelkoop, M., van Os, A. G., Bierma-Zeinstra, S. M.,

& Koes, B. W. (2007). Incidence and determinants of lower extremity running

injuries in long distance runners: a systematic review. Br J Sports Med, 41(8),

469-480; discussion 480.

Wen, D. Y., Puffer, J. C., & Schmalzried, T. P. (1998). Injuries in runners: a prospective

study of alignment. Clin J Sport Med, 8(3), 187-194.

165

5.8 Tables

Table 5.1. Participant demographics.

N Age (years) Height (m) Mass (kg) RRMI 15 37.27±9.30 1.63±0.07 60.69±8.17

INJF 35 39.89±9.52 1.66±0.08 66.54±12.95

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free. Values are represented as – mean (standard deviation)

166

Table 5.2. Group descriptive statistics.

RRMI Group INJF Group

HABD (Nm/kg) 1.14±0.32 1.19±0.25 HEXR (Nm/kg) 0.47±0.07 0.49±0.08

HEXT (Nm/kg) 0.71±0.14 0.70±0.20

HFLX (Nm/kg) 0.79±0.14 0.76±0.17

TFLX (repetitions) 34.73±17.06 27.02±12.04

TEXT (seconds) 188.88±59.16 165.12±71.12

LTFLX (seconds) 68.38±25.99 63.62±25.83

Abbreviations: RRMI, running related musculoskeletal injury; INJF, injury free; HABD, hip abduction; HEXR, hip external rotation; HEXT, hip extension; HFLX, hip flexion; TFLX, trunk flexion; TEXT, trunk extension; LTFLX, lateral trunk flexion. Values are represented as – mean (standard deviation).

167

Table 5.3. Correlations (r) between strength and endurance, and running kinematic variables.

HABD HEXR HEXT HFLX TFLX TEXT LTFLX

Hip r -0.068 -0.178 -0.108 -0.132 0.206 -0.182 -0.162 Adduction p- Angle 0.657 0.217 0.456 0.361 0.152 0.207 0.260 value

r 0.297* 0.215 0.160 0.143 -0.237 0.319* 0.184 Contralateral p- Pelvic Drop 0.036 0.134 0.266 0.322 0.098 0.024 0.201 value

Ipsilateral r -0.097 -0.162 0.016 -0.010 -0.138 -0.198 -0.303* Trunk Lean

p- -0.504 0.260 0.913 0.946 0.340 0.168 0.033 value

* Indicates statistically significant relationship; Abbreviations: HABD, hip abduction; HEXR, hip external rotation; HEXT, hip extension; HFLX, hip flexion; TFLX, trunk flexion; TEXT, trunk extension; LTFLX, lateral trunk flexion.

168

5.9 Figures

Figure 5-1. Hip abduction strength test.

Figure 5-2. Hip external rotation strength test.

169

Figure 5-3. Hip extension strength test.

170

Figure 5-4. Trunk flexor endurance test. A) Starting position.

B) Finish position.

171

Figure 5-5. Trunk extensor endurance test.

Figure 5-6. Lateral trunk flexor endurance test.

172

Figure 5-7. Peak contralateral pelvic drop vs. trunk extensor endurance.

Figure 5-8. Peak contralateral pelvic drop vs. isometric hip abduction strength. 173

Figure 5-9. Peak ipsilateral trunk flexion vs. lateral trunk flexion endurance.

174

References

Alexander, C. J. (1990). Osteoarthritis: a review of old myths and current concepts.

Skeletal Radiol, 19(5), 327-333.

Asay, J. L., Mundermann, A., & Andriacchi, T. P. (2009). Adaptive patterns of

movement during stair climbing in patients with knee osteoarthritis. J Orthop Res,

27(3), 325-329.

Bazett-Jones, D. M., Cobb, S. C., Huddleston, W. E., O’Connor, K. M., Armstrong, B. S.,

& Earl-Boehm, J. E. (2013). Effect of patellofemoral pain on strength and

mechanics after an exhaustive run. Med Sci Sports Exerc, 45(7), 133.

Bazett-Jones, D. M., Cobb, S. C., Joshi, M. N., Cashin, S. E., & Earl, J. E. (2011).

Normalizing hip muscle strength: establishing body-size-independent

measurements. Arch Phys Med Rehabil, 92(1), 76-82.

Beard, M., Bazett-Jones, D., Donovan, L., Thomas, A., & Gribble, P. (2015a). Hip

strength and trunk endurance in injured and injury free runners participating in a

"marathon in training" program: a prospective cohort study. University of Toledo.

175