Abstract
ning economy (RE) is the oxygen utilization during a steady state submaximal running bout. The purpose of this study was two-fold: (a) to determine if running in minimalist footwear results in better RE (mL kg -1 km -1 ) compared to conventional footwear and to identify any relationships between RE and lower limb muscle activation; (b) to determine whether any changes in RE related to minimalist footwear are sustained following exercise-induced fatigue. In a fully randomized, counterbalanced fashion, ten well-trained male distance runners (age 29.0±7.5; BMI 38.6±6.5 kg m -2 ; 2max 61.6±7.3 mL min -1 Kg -1 ) completed a RE test pre- and post- fatigue on a motorized treadmill in both conditions using identical footwear (minimalist 178g; conventional 349g). The fatiguing protocol consisted of high- intensity interval training (7 X 1000-m at 94-97% O2max) on a 200-m, unbanked, Mondo surface, indoor running track. Cardiorespiratory, muscle activation, and kinematic parameters as well as, the rate of perceived exertion and blood lactate were measured throughout the experimental sessions. A significant main effect of footwear on running speed during intervals (p=0.041) was found. Participants ran faster during the minimalist compared to conventional footwear condition (3:24±0:44 vs. 3:30±0:47 (mm:ss), respectively). While fatigue was induced, no other effect of time or footwear on RE, muscle activation or stride frequency occurred. The results of this study suggest that the characteristics of the minimalist footwear did not differ enough from the conventional shoes to induce acute changes in metabolic, kinematic and muscle activation variables during the submaximal runs.
iii Acknowledgments In appreciation of their invaluable support, guidance and patience, I would like to express sincere gratitude to my graduate supervisors Drs. Fabien Basset and Jeannette Byrne. I would also like to thank my colleagues Adeboye Adebayo and Mohammed Saad for their friendship and assistance with data collection, and Dr. Timar (Tim) Alkanani for his tutelage in the exercise physiology laboratory. I would be very remiss if I did not extend a special thanks to my parents for their support. Finally, I am most obliged to my greatest source of support and encouragement, my wife, Courtney. I deeply appreciate her unwavering selflessness as her sacrifices have enabled me to further my education.
iv Table of Contents Abstract ............................................................................................................................. ii Acknowledgments.......................................................................................................... iii Table of Contents............................................................................................................ iv List of Tables ................................................................................................................... vi List of Figures ................................................................................................................. vii List of Abbreviations and Symbols ........................................................................... viii List of Appendices ...........................................................................................................ix Chapter 1: Introduction and Overview ........................................................................1 1.1 Background of Study................................................................................................................................. 1 1.2 Purpose of Study ......................................................................................................................................... 2 1.3 Significance of Study ................................................................................................................................. 3 Chapter 2: Review of Literature ....................................................................................4 2.1 Background .................................................................................................................................................... 4 2.2 Running Economy....................................................................................................................................... 6 2.3 Running Economy and Performance............................................................................................... 8 2.4 Factors that Influence Running Economy .................................................................................... 9 2.5 Runner Characteristics............................................................................................................................ 9 2.6 Running Speed........................................................................................................................................... 10 2.7 Environment............................................................................................................................................... 12 2.8 Spatiotemporal Variables ................................................................................................................... 15 2.9 Ground Reaction Forces ...................................................................................................................... 17 2.10 Foot Strike Patterns ............................................................................................................................ 18 2.11 Fatigue......................................................................................................................................................... 21 2.12 Footwear .................................................................................................................................................... 24 2.12.1 Barefoot ................................................................................................................................................24 2.12.2 Minimalist............................................................................................................................................26 2.12.3 Conventional ......................................................................................................................................27 2.12.4 Does Footwear type Affect Running Economy?..................................................................28 2.12.5 Mass Effect ..........................................................................................................................................31 2.12.6 Shoe Sole Characteristics ..............................................................................................................32 2.12.7 Spatiotemporal..................................................................................................................................34 2.12.8 Foot Strike Pattern ..........................................................................................................................36 2.13 Muscle Activation.................................................................................................................................. 40 2.14 Summary of Footwear ........................................................................................................................ 45 Chapter 3: Materials and Methods............................................................................. 46 3.1 Experimental Procedures ................................................................................................................... 46 3.2 Data Collection .......................................................................................................................................... 51 3.2.1 Rate of Perceived Exertion (RPE) ................................................................................................51 3.2.2 Blood Lactate ........................................................................................................................................51
v 3.2.3 Heart Rate ..............................................................................................................................................51 3.2.4 Muscle Activation................................................................................................................................51 3.2.5 Cardiorespiratory Measurements ...............................................................................................52 3.2.6 Video Data ..............................................................................................................................................52 3.3 Data Analysis & Reduction ................................................................................................................. 53 3.3.1 Metabolic ................................................................................................................................................53 3.3.2 Heart Rate ..............................................................................................................................................54 3.3.3 Video.........................................................................................................................................................54 3.3.4 Electromyography ..............................................................................................................................55 3.4 Statistical Analysis .................................................................................................................................. 55 Chapter 4: Results ......................................................................................................... 56 4.1 Participant Characteristics ................................................................................................................ 56 4.2 Participant Training Profile .............................................................................................................. 57 4.3 Exercise-Induced-Fatigue ................................................................................................................... 58 4.4 Metabolic and cardiorespiratory parameters ........................................................................ 61 4.5 Kinematics ................................................................................................................................................... 62 4.6 Electromyography................................................................................................................................... 62 Chapter 5: Discussion ................................................................................................... 64 5.1 Characteristics and Training Status ............................................................................................. 64 5.2 Exercise-induced-fatigue .................................................................................................................... 65 5.3 Metabolic ...................................................................................................................................................... 68 5.4 Kinematics during Submaximal Running Trials ................................................................... 74 5.5 Muscle Activation .................................................................................................................................... 74 5.6 Methodological Considerations....................................................................................................... 78 5.7 Future Research ....................................................................................................................................... 79 Chapter 6: Conclusions................................................................................................. 81 6.1 Response to Hypotheses...................................................................................................................... 81 6.2 Summary....................................................................................................................................................... 82 Bibliography................................................................................................................... 83 Appendices ................................................................................................................... 105 Appendix A: Training profile questionnaire ................................................................................ 105 Appendix B: Borg 6-20 Rate of perceived exertion (RPE) scale ........................................ 106
vi List of Tables TABLE 4.1: SUMMARY OF THE PARTICIPANTS’ CHARACTERISTICS AND TRAINING PROFILE. .................................................................................................................. 58 TABLE 4.2: METABOLIC RESPONSES ACROSS FOOTWEAR AND FATIGUE CONDITION .................................................................................................................................. 62 TABLE 4.3: SAGITTAL KINEMATIC RESPONSES ACROSS FOOTWEAR AND FATIGUE CONDITIONS ............................................................................................................ 62 TABLE 4.4: INTEGRATED EMG RESPONSES ACROSS FOOTWEAR AND FATIGUE CONDITIONS ............................................................................................................ 63 TABLE 4.5: ROOT-MEAN-SQUARE EMG RESPONSES ACROSS FOOTWEAR AND FATIGUE CONDITIONS. ........................................................................................... 63
vii List of Figures FIGURE 3.1: EXPERIMENTAL DESIGN AND TIME LINE. .............................................. 48 FIGURE 4.1: LACTATE PRODUCTION, RPE SCORE, AND HR AS A FUNCTION OF TIME DURING EIF.. .......................................................................................................... 60 FIGURE 4.2: RUNNING PACE AS A FUNCTION OF TIME DURING EIF.. ...................... 61
viii List of Abbreviations and Symbols CR Cost of running EIF Exercise induced fatigue EMG Electromyography HIIT High-intensity interval training HR Heart rate MAS Maximal aerobic speed MI Minimalist index MIN Minimalist footwear MVC Maximum voluntary contraction RE Running economy RER Respiratory exchange ratio RPE Rate of perceived exertion SHOD Conventional running shoes 2 Volume carbon dioxide output 2 Volume oxygen uptake
ix List of Appendices APPENDIX A: TRAINING PROFILE QUESTIONNAIRE .................................................105 APPENDIX B: BORG 6-20 RATE OF PERCEIVED EXERTION (RPE) SCALE ...........106
1 Chapter 1: Introduction and Overview 1.1 Background of Study Running is one of the most prevalent activities for both sporting and fitness purposes. Despite the high popularity of conventional running shoes (SHOD) historically, there is currently a shift towards minimalist footwear (MIN) the characteristics of which are in complete contrast to (Fleming, Walters, Grounds, Fife, & Finch, 2015; McCallion, Donne, Fleming, & Blanksby, 2014; Sobhani et al., 2014). Designed to be lightweight with modest cushioning and motion-control technologies, the belief is that their use will positively impact a runner’s health and performance via improvements in running economy (RE) (Jenkins & Cauthon, 2011; Rothschild, 2012). However, relatively little is known about how the minimalist models of footwear impact running economy and there are conflicting reports within the scientific community (Jenkins & Cauthon, 2011; Paulson & Braun, 2014). Running economy is an accepted physiological parameter for efficient distance running performance and is thought to be a greater predictor than the previous “gold standard” O2max (Anderson, 1996; Conley & Krahenbuhl, 1980; Daniels, Oldridge, Nagle, & White, 1978). Defined as the rate of oxygen uptake 2) at a given submaximal running velocity (Daniels & Daniels, 1992; Morgan & Craib, 1992), RE is expressed as the 2 per unit of mass (kg) relative to the distance covered (km) or time (min). More specifically, RE is the submaximal, steady-state
2 rate of oxygen uptake (Altman & Davis, 2012; Gruber, Umberger, Braun, & Hamill, 2013; Pinnington & Dawson, 2001). Although there is a shift towards the use of MIN with the belief that they will positively impact running performance (McCallion et al., 2014; Sobhani et al., 2014), conclusive reports of how MIN influence running performance, and more specifically RE, represent a gap within the scientific literature. However, there is a well-established body of research on the mass effect of footwear that reports a positive relationship between footwear mass and energy expenditure (Cheung & Ngai, 2016; Fuller, Bellenger, Thewlis, Tsiros, & Buckley, 2015). Additionally, the interrelationship between fatigue, footwear, and RE is also not well understood. 1.2 Purpose of Study This study aims to determine if there is an effect of minimalist shoes on RE and if it is altered by exercise-induced fatigue (EIF). It also seeks to identify if changes in RE are reflected by differences in muscle activation as quantified using electromyography (EMG). As such, the research question is organized into the following sub-questions: A) What is the effect of minimalist footwear on RE? B) Do muscle activation patterns reflect these differences? C) Is there a change in RE with fatigue? D) Is there an attenuation of fatigue in minimalist shoes? The hypothesis is that wearing minimalist shoes will lead to a lower oxygen uptake at a submaximal speed resulting in improved RE, in both the non-fatigued
3 and fatigued states. It was also hypothesized that the 2 will reflect the differences in mass between footwear conditions and changes in muscle activation amplitude will reflect the metabolic differences. No shoe effect on EMG is expected, however, a fatigue effect is. 1.3 Significance of Study Although a substantial number of studies (De Wit, De Clercq, & Aerts, 2000; Greensword, Aghazadeh, & Al-Qaisi, 2012; Lieberman et al., 2010; Olin & Gutierrez, 2013) demonstrate changing footwear will alter kinematics, muscle activation and other variables that influence RE, the majority of these studies were conducted without the use of MIN. Inconsistent reports of the effects of wearing MIN on RE and muscle activation present a gap within the literature (Kahle, Brown, Shaw, & Shaw, 2016; Kasmer, Ketchum, & Liu, 2014; Khowailed, Petrofsky, Lohman, & Daher, 2015; Rao, Chambon, Guéguen, Berton, & Delattre, 2015; Sobhani et al., 2014; Squadrone & Gallozzi, 2009). Fatigue is also known to influence the aforementioned characteristics, but few direct observations on RE have been identified (Collins et al., 2000; Guezennec, Vallier, Bigard, & Durey, 1996; Xu & Montgomery, 1995; Zavorsky, Montgomery, & Pearsall, 1998), none of which used MIN. Therefore, the manifestation of fatigue while wearing minimalist compared to conventional footwear represents another gap within the literature. With growing participation in running activities each year and a high prevalence of running-related injuries per year between 19-79% (van Gent et al., 2007), it is of no surprise that a large breadth of research has focused on footwear
Description
The study examines how minimalist shoes affect running economy and muscle activation in distance runners.