SELECfED METABOLIC RESPONSES TO SKATEBOARDING A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWArI IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN KINESIOLOGY AND LEISURE SCIENCE AUGUST 2004 By Ian K. Hunt Thesis Committee: Ronald K. Hetzler, Chairperson Iris F. Kimura Jan Prins iii ACKNOLEDGMENTS Thank you Lia. Your unconditional support and encouragement made this all possible. Mom and Dad, your role in this achievement began the day I was born. Ronald K. Hetzler, thank you for the countless early morning hours and guidance through the world of exercise physiology. Iris F. Kimura, I'll miss our short office chats. Jan Prins, thank you for all of your technical guidance. Lastly, I couldn't have done it without the many subjects who volunteered their time. iv ABSTRACf SELECfED METABOLIC RESPONSES TO SKATEBOARDING by Ian KHunt Master of Science University of Hawai'i at Manoa Major Advisor: Ronald K. Hetzler PURPOSE: This study used oxygen uptake (V0z) and heart rate (HR) responses to a skateboard treadmill test (TT) to estimate the metabolic responses to skateboarding during a field test (FT). METHODS: Ten skateboarders (age = 24.5 :l:: 3.1 yr.; weight = 1 74.2 :l:: 8.3 kg; height =176.2 :l:: 6.6 em; V02max =53.7 :l:: 5.2 ml·kg-1·min- ) participated in the TT and the FT. The FT consisted of 30-minutes of skateboarding while wearing a heart rate monitor. The HR data from each FT were used to estimate VOz. RESULTS: The mean VOz for 30-minutes of skateboarding was estimated to be 28.6 ± 2.3 ml·kg-1·min-1. The mean caloric expenditure, assuming a mixed diet, was 308.6 ± 37.9 1 kcal (10.3 ± 1.3 Kcal·min- ). CONCLUSION: These data indicated that skateboarding could provide an adequate stimulus for increasing cardiorespiratory endurance and the intensity of self paced skateboarding may be adequate for inclusion in a weight management program. v TABLE OF CONTENTS Acknowledgments iii Abstract iv List ofTables vi List of Figures , vii Part I Selected Metabolic Responses to Skateboarding Introduction 1 Methods 3 Subjects: 3 Treadmill Tests: 3 Skateboard Treadmill Test Protocol: 4 Development of the Skateboard Treadmill Protocol: 5 Field Tests: 5 Metabolic Measurements: 6 Field Test Estimations and Calculations: 6 Ratings of Perceived Exertion (RPE): 7 Statistical Analysis: 7 Results 8 Physical Characteristics: 8 Metabolic Measures: 8 Heart Rate (HR) Oxygen Uptake Relationship: 10 Field-Tests (FT): 11 Differentiated Ratings of Perceived Exertion: 13 Discussion 14 Conclusion '" : 24 Part II: Review of Literature Skateboarding: 25 Differentiated Ratings of Perceived Exertion: 28 Factors That Influence the HR-V02 Relationship: 33 Energy Expenditure: '" 39 Appendix A. Raw Data Tables 48 Abbreviations 48 Appendix B. Forms 66 Informed Consent 67 Medical History Questionnaire 70 Par-Q 72 Skateboard Skill Assessment 73 Subject Letter 74 Appendix C. Statistics 75 References 93 vi LIST OF TABLES 1. Subject Characteristics 8 2. Skateboard Treadmill Test Metabolic Data 9 3. Individual HR-V02 Correlation Values 10 4. Individual Values From The Field-Test. 12 5. Individual V02 Reserve and Individual Estimated Mean V02 From Field-Test 13 6. Raw Data Tables 48 vii LIST OF FIGURES Figure Page 1. Heart Rate and Estimated V02 During Field Test 16 2. Relationship of Mean Values for V02 and Heart Rate 17 3. Individual Subject HR-V02 Relationships 18 4. RPE Subjects 1-5 23 5. RPE Subjects 6-10 23 1 PART I SELECTED METABOLIC RESPONSES TO SKATEBOARDING Introduction This study was undertaken to investigate selected physiological responses to the sport of skateboarding. Participation in skateboarding has increased dramatically over the last decade; however, little is known about its potential to impact physical fitness. The National Sporting Goods Association reported in 1992 that 5.5 million individuals participated in skateboarding more than once. In 2002, it was reported that this number had increased to 9.7 million, a 75% increase over the last decade (NSGA, 2002). Therefore, annual participation in skateboarding is similar to tennis (11 million) and volleyball (11.5 million), and skateboarding participation exceeds alpine skiing (7.4 million) and snowboarding (5.6 million) (NSGA, 2002). It was estimated that 5.8 million children and adolescents under the age of 18 had participated in skateboarding in 1996, and an estimated 750,000 participated on a weekly basis (CIPP, 2002). In the past 25 years the annual incidence of skateboarding related injuries requiring medical treatment have risen and fallen. Annual injuries peaked in 1977 at 150,000, fell in 1983 to 16,000, rose in 1994 to 24,000 in individuals under the age of 20, and rose again to about 51,000 in 1999 (CIPP, 2002). Although these numbers appear alarming, Kyle et al. (2002) using participation exposure based estimates revealed that, in 1998, the rate of emergency department treated (ED) injuries were 8.9 injuries per 1000 participants. This value is twice tharof "in-line" skating (3.9 per 1000), and 2 approximately half that of basketball (21.2 per 1000) and football (20.7 per 1000). Consequently, Kyle et al. (2002) concluded that skateboarding is a comparatively safe sport. With millions of children participating in skateboarding world wide, there is a surprising lack of research on the sport. A search on the PubMed® database revealed 48 studies relating to skateboarding injuries and one paper from 1980 examining the biomechanical aspects of the sport. It appears that no metabolic research has been published on skateboarding. Therefore, the rise in the popularity of skateboarding, coupled with the absence of published works examining the metabolic responses to skateboarding,, indicates further study is warranted. The purpose of the present study was to examine the following questions: (1) will skateboarding in the field at a self selected pace elicit exercise responses sufficient to increase aerobic fitness; and, (2) is skateboarding a beneficial mode ofexercise for someone who is trying to lose or manage their weight? This was accomplished by: first, establishing an individual heart rate oxygen uptake relationship during an incremental skateboard treadmill test; and second, using heart rate data collected during a 30-minute field test and oxygen uptake data from the skateboard treadmill test to estimate the metabolic responses to skateboarding in the field. In addition, differentiated ratings of perceived exertion data were gathered during the skateboard treadmill test in order to examine the effect the different roles the two legs have on perception of effort. 3 Methods Subjects: Eight males and two females volunteered to participate in the study (age =24.5 ± 3.1 yr; weight =74.2 ± 8.3 kg; height =176.2 ± 6.6 cm; % fat =11.5 ± 6.2 %; VOzmax = 53.7 ± 5.2 ml-kg-1-min-1)(mean ± SD). Height was determined using a stedometer and weight was determined using a Detecto® scale (model 442). Skinfolds were taken using a Lange caliper and body composition was estimated from the sum of seven skinfolds (Jackson and Pollock, 1985). The subjects included nine recreational and one professional skateboarder (Gravity Games gold medalist in the four-man downhill event). Subjects were required to fill out a questionnaire to determine if their skill level was adequate to safely participate in the study. The criteria in the questionnaire included: at least one year of experience skateboarding, the ability to perform an "Ollie" (a fundamental trick that allows the skateboarder to jump, maintaining contact with the board, and land under control), and the ability to skate for an hour without taking a break. If the criteria were met, subjects were required to participate in a practice session to familiarize them selves with skateboarding on a treadmill. All subjects were able to safely skateboard on the treadmill. Written consent was obtained in compliance with the Institutional Review Board's Committee On Human Studies. Treadmill Tests: The subjects participated in two treadmill tests separated by at least 48 hours. During the first visit to the laboratory, anthropometric measures were taken, the subjects participated using the standard Bruce Protocol to determine V02max while running, and 4 they had an opportunity to practice skateboarding on the treadmill. During the second visit, subjects participated in the skateboard treadmill test. Skateboard Treadmill Test Protocol: All laboratory protocols were conducted on a Quinton Medtrack T65 treadmill. The 10 stages of the treadmill test were as follows: stage 1 consisted of skateboarding at 134 memin-1 (5 mph) at 0% grade; stage 2 consisted of 134 memin- 1 at 1.5% grade; in the subsequent 8 stages speed was incrementally increased by 13.4 memin- 1 (0.5 mph) while remaining at 1.5% grade. The final stage, stage 10, was performed at 241.2 memin- 1 (9 mph) at 1.5% grade. Each stage consisted of three minutes of skateboarding followed by 30 seconds of rest. While skateboarding, the subjects' legs performed different functions. One leg, the support leg, supported the weight of the body; while the other leg, the kicking leg, was used to propel the body forward. Once the subject gained enough momentum, the kicking leg was placed back on the skateboard. At this point the kicking leg and support leg were both used to support the weight of the body (support position). As the skateboard slowed, the subject resumed kicking in order to maintain their position on the treadmill. During the 3-minute stages, the subjects were not required to kick continuously. They were allowed to assume the support position and coast for a few seconds, thus relieving the stress on the support leg. They were also required to kick with the same leg throughout the entire test.