Dr. Robert Robergs Fall, Dr. Robert A. Robergs, Ph.D., EPC, FASEP. Director: Exercise Physiology Laboratories

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1 Dr. Robert Robergs Fall, VO max Measurement and Analysis Dr. Robert A. Robergs, Ph.D., EPC, FASEP Director: Exercise Physiology Laboratories Exercise Science Program The University of New Mexico Albuquerque, NM Early History In running the oxygen requirement increases continuously as the speed increases,.; the actual oxygen intake, however, reaches a maximum beyond which no effort can drive it. The oxygen intake may attain its maximum and remain constant merely because it cannot go any higher owing to the limitations of the circulatory and respiratory system. Archibald Vivian Hill (Hill A.V. and H. Lupton. QQ J Med 9; 6:5-7.) In performing his research, Hill used, 6-7 subjects limited running speeds discontinuous running protocols combined data from multiple subjects VOmax Issues

2 Dr. Robert Robergs Fall, What is VO max VO max VO Cardiorespiratory limitations Duration should be ~8- min Time or Intensity Definitions: The maximum rate oxygen can be taken in (pulmonary), transported (circulatory), and utilized (peripheral) for energy production. The maximal rate at which the body can consume oxygen during exercise. Other less correct terms! aerobic power aerobic capacity maximal cardiorespiratory capacity VOmax Issues

3 Dr. Robert Robergs Fall, Powers and Howley, 997, p: 5 VO max represents the physiological ceiling for the ability of the oxygen transport system to deliver O to contracting muscles. Wilmore and Costill, 99, p:. Oxygen consumption peaks and remains constant or drops slightly, even though work intensity continues to increase. The best single measurement of cardiorespiratory endurance and aerobic fitness. VOmax Issues

4 Dr. Robert Robergs Fall, Robergs and Roberts, 998, p: 7 the maximal rate that the body can consume oxygen during exercise detected as a plateau despite further increases in exercise intensity... VOmax Issues

5 Dr. Robert Robergs Fall, Determinants of VO max CENTRAL PERIPHERAL HR x SV Cardiac Output A-aPO SaO [Hb] oxygen delivery VO max = Qmax x a-vo max capillary density PO gradients muscle mass fiber dimensions O supply demand relationships Peripheral Oxygen Diffusion VOmax Issues 5

6 Dr. Robert Robergs Fall, Plateau??? VO (ml/min) Subject # Subject # Clear plateau For subjects, breath-by-breath data with an breath average, and based on VO 5 ml/min for VO max and closest neighboring data point. VO plateau incidence = 86% Background No universally recommended procedures for processing VO data from breath-by-breath indirect calorimetry, or from time averaged systems. No standardized criteria or recommended methods for detecting either of a VO plateau, the maximal rate of oxygen consumption (VO max), or a peak VO in the absence of a VO plateau (VO peak). Increasing use of breath-by-breath indirect calorimetry in education, research and professional practice The lack of any objective criteria to follow when processing decreases the validity of measurement. VOmax Issues 6

7 Dr. Robert Robergs Fall, Challenges How do researchers in exercise physiology currently collect and process data? How long should the protocol be? What type of protocol should be used? What causes the noise in breath-by-breath VO data? Should this noise be reduced? If so, how? What is a VO plateau? How can a VO plateau be objectively determined? What is VO max vs. VO peak? How can VO max and VO peak be objectively determined? What causes the noise in breath-by-breath VO data? L/min, with a range of.. L/min VE STPD (L/min) VOmax Issues 7

8 Dr. Robert Robergs Fall, Variability 96 % explained by a twofactor model of VE and FEO Measured Predicted Predicted. Pred VO =.957(Meas VO ) R =.957 SEE =.59 L/min) Measured VO (L/min) 6 8 Variability Remaining %error. 6 8 VOmax Issues 8

9 Dr. Robert Robergs Fall, Should this noise be reduced? YES How should this noise be reduced?.5 a=bb. b=5 s Time Averaging e Breaths 6 s s c= s d=6 s 5 s VOmax Issues 9

10 Dr. Robert Robergs Fall,.5 a=bb c= breaths 5 b=5 breaths 5 5 d= breaths Time Interval (min) Breath Averaging breaths breaths.5 5 breaths.5 bb a muscle d Digital Filtering b cardiovascular e c ventilation Data Points Data Points VOmax Issues

11 Dr. Robert Robergs Fall, Digital Filter Example What is a VO plateau? VO (ml/min) VO (ml/min) rest exercise linear regression VO plateau at VO max initial deviation from linearity VOmax Issues

12 Dr. Robert Robergs Fall, 5 What is VO max or VO peak? Data Example treadmill running VO (ml/min) VOmax Issues

13 Dr. Robert Robergs Fall, Conclusions Clear rationale for processing breath-by-breath VO data to decrease noise. Processing best done by digital filtering Still formulating and debating criteria and methods to quantify VO plateau, VO max, VO peak In the absence of a VO plateau, what are valid criteria to use to verify a true VO max? VOmax Issues