A Thesis entitled Effects of Playing Surface on Muscle Activation and Plantar Pressure in Collegiate Football Players by Ema Kossin Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Masters in Science Degree in Exercise Science with a Concentration in Athletic Training _________________________________________ Dr. Neal Glaviano, Committee Chair _________________________________________ Dr. Grant Norte, Committee Member _________________________________________ Dr. Cindy Bouillon, Committee Member _________________________________________ Dr. Amanda Bryant-Friedrich, Dean College of Graduate Studies The University of Toledo May 2018 Copyright 2018, Ema Leigh Kossin 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 Effects of Playing Surface on Muscle Activation and Plantar Pressure in Collegiate Football Players by Ema Kossin Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Exercise Science The University of Toledo May 2018 Context: Research has evaluated if there are differences in injury rates on different playing surfaces. While it is unclear why these differences are occurring, altered muscle activity and plantar pressure have been suggested. Objective: To determine if differences occur in muscle activation and plantar pressure on different surfaces during functional activity. Design: Crossover study. Setting: Laboratory and two football fields. Patients or Other Participants: Nine division I football. Interventions: Participants completed three functional tasks (sprint, jog, and cut) on three different surfaces (turf, grass, and lab). Main Outcome Measures: Mean muscle activation of the lower extremity was recorded with surface electromyography (EMG). Plantar pressure recorded mean pressure and pressure-time integral (PTI). Participants completed the functional tasks on all surfaces. A repeated measures ANOVA for each dependent variable was performed, with a priori of (p<0.05). Results: There was some statistical difference in the mean EMG. During the jogging task, the gluteus medius differed on the laboratory and the turf (p=.016), and the peroneus longus between the grass and the turf (p=.029). During the cutting task, the peroneus longus differed on the grass compared to the turf (p=0.038). iii During the sprinting task, the biceps femoris differed on the grass compared to the turf (p=.011). During the cutting task, the PTI differed between the turf and the grass (p=.044). Conclusions: There were differences in muscle activation in the lower extremity across all three surfaces. Greater differences were seen in the distal muscles. There was no significance in the mean pressure of the plantar pressure force distributions. This new information could influence how clinicians rehabilitate lower extremity injuries and return to play decisions. More research will need to be done to identify if these differences observed match up with previous studies on injury rate differences. Word Count 291 iv Table of Contents Abstract iii Table of Contents v List of Tables vii List of Figures viii List of Abbreviations ix List of Symbols x I. Manuscript 1 A. Introduction 1 B. Methods 2 a. Study Design 2 b. Participants 2 c. Instrumentation 3 d. Procedures 4 e. Data Analysis 5 f. Statistical Analysis 5 C. Results 6 D. Discussion 6 E. Conclusion 11 References 12 Appendices v A. The Problem 21 B. Literature Review 25 C. Additional Methods 36 D. Additional results 62 E. Back Matter 82 F. Bibliography 85 vi List of Tables Table 1 Differences in EMG Activity During the Jogging Task .................................15 Table 2 Differences in EMG Activity During the Cutting Task ..................................16 Table 3 Differences in EMG Activity During the Sprinting Task ...............................17 Table 4 Differences in Plantar Pressure Activity During the Functional Tasks ...........18 Table 5 Weather Log during Collection .......................................................................19 vii List of Figures Figure 1 Flowchart of functional tasks across the three playing surfaces .....................20 viii List of Abbreviations ACL............................Anterior Cruciate Ligament ATFL..........................Anterior Talofibular Ligament CAI .............................Chronic Ankle Instability CFL ............................Calcaneofibular Ligament EMG ...........................Electromyography FIFA ...........................Fédération Internationale de Football Association FTCL ..........................Fibulotalocalcaneal Ligament IER .............................Inferior Extensor Retinacula IMU ............................Inertial Measurement Units IT ................................Illiotibial kPa Kilopascal kPa*s ..........................Kilopascal per second LCL ............................Lateral Collateral Ligament LTCL..........................Lateral Talocalcaneal Ligament MCL ...........................Medial Collateral Ligament NCAA ........................National Collegiate Athletic Association NFL ............................National Football League PCL ............................Posterior Cruciate Ligament PTFL ..........................Posterior Talofibular Ligament PTI..............................Pressure Time Integral ix List of Symbols #..........p<0.05 when compared to the lab *.......... p<0.05 when compared to the grass †..........p<0.05 when compared to the turf x Chapter One Manuscript Introduction Every day millions of people participate in athletic related activities; from professional athletes completing at the elite level, to weekend warriors just having fun with friends. Several sports such as football, soccer, and lacrosse are played predominantly outdoors; however, the playing surface is not always the same. The playing surface can change between natural grass and artificial turfs. With athletes changing playing surfaces during the course of a season, it has been found that injury rates change based on the playing surface.1,2 With more injuries occurring on artificial turf than on grass.1,2 In sports such as football, soccer, and lacrosse there are two types of injuries that can occur: contact injuries and noncontact injuries.3 Contact injuries are a result of player-to-player contact, and most likely not influenced too much by the playing surface.3 Noncontact injuries are when the player is injured during participation and it is not due to collision with another player. Many factors can lead to this type of injury such as: overuse, sport specific movements, and force distributions on different joints due to muscle activation and plantar pressure distributions.4,5 Majority of noncontact injuries that occur are lower extremity injuries. Ninety-two percent of all muscle injures and fifty-three percent of all injuries occur to the lower extremity.3,6 Previous studies have found a five percent increase in lower extremity injuries when soccer was played on artificial turf when compared to grass.7 As well as a thirty-eight percent increase in overuse injuries when played on artificial turf when compared to natural grass.2 This could be due to differences in muscle activation occurring on the turf compared to the natural grass or any other training surface. Knowing that players are occurring injuries at different rates when they play on artificial turf as compared to playing on natural grass, something has to be changing with how the athlete’s body is responding to the playing surface. However, there is no literature when it comes to how a person’s body responds to different playing surfaces; this includes the laboratory setting, where most rehabilitation will 1 occur if a person is injured. It is still unclear in the literature if there is a difference in plantar pressure distributions and muscle activation on different playing surfaces. Hence the purpose of this study is to determine if performing different functional tasks on artificial turf, natural grass, and in the laboratory setting affects the muscle activation and plantar pressure of the lower extremity in collegiate football players. Methods Study Design: This study was a crossover study design with the interventions being the same for all participants. The independent variables were playing surface conditions: (1) natural grass, (2) artificial turf, and (3) laboratory setting; during three different functional tasks: (1) 10-yard jog at 50%, (2) a ten-yard jog at 100%, and a (3) ten-yard jog at 50% with a cutting task being performed off the dominant leg. The surfaces were tested in a randomized predetermined order, and the functional tasks were performed in the randomized predetermined order. The dependent variables were electromyography (EMG) peak and mean for eight lower extremity muscles, and plantar pressure readings of mean pressure and pressure-time integral. Participants Volunteers were recruited from the University of Toledo athletics department. A convenience sample of 9 male participants (age: 20.42.0 years, height: 72.9 2.5 cm, and mass: 93.712.3 kg) were enrolled. Participants were enrolled if they met the inclusion criteria: between 18 and 25 years old, and participated on the University of Toledo football team. Exclusion criteria were any lower extremity injury within the past six months, any low back injury within the past six months, any history of having a lower extremity surgery, and a men’s