Examination of a Self-Selected Speed Graded Exercise Test using an Automated Treadmill as a Valid Means to Measure VO2max DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Cory Martin Scheadler Graduate Program in Education: Physical Activity & Educational Services The Ohio State University 2013 Dissertation Committee: Dr. Steven Devor, Advisor Dr. Timothy Kirby Dr. Robert Hamlin Copyrighted by Cory Martin Scheadler 2013 Abstract The use of graded exercise tests for measuring maximal oxygen consumption (VO2max) is common practice in cardiopulmonary medicine. Limitations to VO2max are still being debated despite the concept being founded nearly a century ago. It has been suggested that measuring VO2max using traditional protocols (TP) does not allow for proper investigation of all theories of limitations to oxygen consumption, whereas allowing subjects to self-select their work rate does. Conflicting results exist in the literature for whether allowing subjects to self-select their work rate (SP) has resulted in a different VO2max compared to TP. Limitations to these studies include the use of a cycling modality and lack of well-trained subjects. Secondary criteria need to be investigated for their validity in discriminating VO2max from VO2peak in SP and TP. Purpose: The purpose of the study was to examine the validity of a self-selected work rate protocol (SP) using an automated treadmill for measuring cardiorespiratory fitness by A) determining whether it allowed individuals to choose their own pace to match a predetermined effort, and B) comparing VO2max from the SP to values obtained from a TP. Secondary criteria were evaluated for their ability to discriminate a VO2max from VO2peak in both SP and TP. Methods: Thirteen experienced endurance runners completed three maximal exercise tests to determine VO2max. Oxygen consumption was measured using a computerized system and averaged over 30 second time periods. SP was completed using an automated treadmill. The automated treadmill consisted of a ii sonar range finder, microcontroller, and customized computer software. Subject deviations from the middle of the treadmill belt resulted in rapid, graded increases or decreases in speed. Secondary criteria of VO2max were assessed using blood lactate (LA), respiratory exchange ratio (RER), and rating of perceived exertion (RPE). Results: Peak work rate achieved during SP was significantly greater than that achieved during TP - by 1.2 METs, p < .05, d = .564. VO2 was significantly greater in TP (64.9 ± 8.2 ml*kg 1*min-1) than SP (63.4 ± 7.8 ml*kg-1*min-1), p < .005, d = .195. All secondary criteria were sensitive measures in both SP and TP; however, according to predictive values and likelihood ratios no criterion had values suggesting they were strongly linked to the condition. Conclusion: Although an automated treadmill allowed subjects to self-select their work rate, SP in combination with an automated treadmill is not yet a valid means of assessing cardiorespiratory fitness. The secondary criteria investigated here are not a suitable means of discriminating VO2max from VO2peak in SP or TP. iii Acknowledgments I need to thank all of those that helped me throughout this project and graduate school in general. I first need to begin with my wonderful wife, Ashlee, who graciously agreed to let me go to graduate school before we really understood the time and effort it would take for both of us. I want to thank my family for all of their love and support throughout the years. I thank my current and past advisors, Steven Devor and Tim Kirby, who have offered their great advice and friendship along the way. To all of those faculty and staff (Bob Hamlin and Kay Yeager, especially), graduates, and undergraduates who I have befriended and given me new perspectives on school and life, I thank you. I want to end with a special thank you to a little guy who reminded me to relax and clear my head by forcing me to play with Legos and go to the park; Aven you helped your daddy more than you will know. iv Vita November 1982 ..............................................Born, West Union, OH June 2001 .......................................................Sardinia Eastern High School August 2005 ...................................................B.S. Biological Sciences, Wright State University January 2006 to Present .................................Graduate Teaching Associate, Department of Health and Exercise Science, The Ohio State University August 2009 ...................................................M.A. Exercise Science, The Ohio State University Publications Scheadler, C.M., N.W. Saunders, N.J. Hanson, and S.T. Devor. Palm Cooling does not Improve Running Performance. Int. J. Sports Med. http://dx.doi.org/10.1055/s-0032- 1327576, 2013. Scheadler, C.M., M.J. Garver, T.E. Kirby, and S.T. Devor. Glycerol Hyperhydration and Endurance Running Performance in the Heat. JEPonline. 13(3): 1-11, 2010. v Fields of Study Major Field: Education: Physical Activity & Educational Services vi Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1: Introduction ....................................................................................................... 1 Chapter 2: Review of Literature ........................................................................................ 8 Introduction ..................................................................................................................... 8 Protocol Design ............................................................................................................... 9 VO2 Plateau ................................................................................................................... 16 Secondary Criteria ......................................................................................................... 21 Blood Lactate ............................................................................................................. 22 RER ........................................................................................................................... 25 Heart Rate .................................................................................................................. 28 RPE ............................................................................................................................ 31 vii Conclusion ................................................................................................................. 34 Verification Phase Protocol ........................................................................................... 35 Sampling Time Interval ................................................................................................. 37 Potential Limiters to VO2max ....................................................................................... 44 Ventilation ................................................................................................................. 45 Alveolar to Arterial Oxygen Transfer ....................................................................... 48 Cardiac Output ........................................................................................................... 48 Muscle Capillary to Mitochondria Oxygen Transfer ................................................ 56 Skeletal Muscle Metabolism ..................................................................................... 56 Conclusion ................................................................................................................. 57 Central Governor Model ............................................................................................... 57 Conclusion ..................................................................................................................... 70 Chapter 3: Self-Selected Work Rate Protocol Validity .................................................... 72 Introduction ................................................................................................................... 72 Methods ......................................................................................................................... 73 Familiarization ........................................................................................................... 74 Maximal exercise ....................................................................................................... 74 Automated Treadmill ................................................................................................. 77 Speed ......................................................................................................................... 79 viii Work rate ..................................................................................................................