1. The concept of VO2max
BASSETT, DAVID R. JR.; HOWLEY, EDWARD T Maximal oxygen uptake: classical versuscontemporary viewpoints. Medicine & Science in Sports & Exercise: Volume 29(5) May 1997 pp

2. Debate
Over the past 10 years there has been a debate about the underlying tenants of VO2max
The O2 plateau
O2 delivery and limitation of VO2max
O2 uptake and limitation of VO2max
Muscle factors as the primary limiters of VO2max

3. Classical View of VO2max
What is VO2max
Maximal rate at which body can take up and utilize O2
Originally described by Hill in 1923
Plotted Running speed vs O2 requirement
Determined there was a VO2max that was limited by cardiovascular and respiratory systems

4. Data from Hill’s VO2 experiments

5. Plots of Running Speed vs VO2, Ve and RQ (RER)
Figure 2-Relationship between speed of running and (a) oxygen intake, (b) lung ventilation, and (c) respiratory quotient. Original graph from . Hill, A. V., C. N. H. Long, and H. Lupton. Muscular exercise, lactic acid and the supply and utilisation of oxygen-parts VII-VIII. Proc. Roy. Soc. B. 97:84-138, 1924.

6. Hill argued
“In running the oxygen requirement increases continuously as the speed increases, attaining enormous values at the highest speeds; 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... “
Hill, A. V. and H. Lupton. Muscular exercise, lactic acid, and the supply and utilization of oxygen. Q. J. Med. 16: , 1923
This has since been referred to as the “plateau” in VO2 at max

7. Figure 3-Relationship of oxygen uptake to work rate during a discontinuous maximal exercise test, showing that some subjects achieve a plateau whereas others do not. Original data from reference 3 . Åstrand, I., P.-O.Åstrand, and K. Rodahl. Maximal heart rate during work in older men. J. Appl. Physiol. 14: , 1959.

8. The VO2 plateau
Now, it appears as though not all subjects achieve a VO2 plateau
Depends on mode of testing and criteria for plateau
E.g. 50, 80 or 150 ml/min
And time of averaging

9. Robergs, R.A. AN EXERCISE PHYSIOLOGIST’S “CONTEMPORARY” INTERPRETATIONS OF THE “UGLY AND CREAKING EDIFICES” OF THE VO2MAX CONCEPT. Journal of Exercise Physiologyonline .2001; 4(1), 1.

10. Limits on VO2max
Another point of controversy regards the question of what limits VO2max
Central or peripheral
Heart, lungs, capillaries or muscle
In general, it is believed that VO2max is limited by the ability of the cardiovascular system to deliver blood, and hence O2, to the tissues

11. TABLE 2. Summary of previous studies examining maximal oxygen uptake in leg versus combined arm-and-leg exercise. Adapted from Shipe(65).

12. Role of Muscle Mass
It is necessary to use the largest muscle mass possible to elicit a true VO2max
Exercise using small muscle masses do not elicit VO2max
Since VO2 is directly proportional to work, it might be expected that using more muscle mass would elicit proportionally more O2 consumption
Max work is limited using large muscle mass vs small

13. Figure 5-Evidence that the heart's capacity to supply blood flow to active muscle is limited. When heavy exercise is performed with the legs, the addition of arm work causes a reduction in both leg blood flow and leg oxygen uptake (not shown). During combined arm-and-leg work, the muscle's capacity to vasodilate exceeds the ability of the heart to supply blood flow. Data of reference 62 . Secher, N. H., J. P. Clausen, K. Klausen, I. Noer, and J. J. T. Central and regional circulatory effects of adding arm exercise to leg exercise. Acta. Physiol. Scand. 100: 1979 as shown in reference 58 . Rowell, L. B. Human Circulation: Regulation During Physical Stress. New York: Oxford University Press, 1986.

14. Blood flow limitation When adding arm exercise to leg
Blood flow is reduced to legs
Total body O2 may increase with workload, but reduction in blood flow will ultimately limit exercise capacity with legs
Cardiac output increases just the same
Therefore the ability of the circulation to vasodilate outstrips the ability of the heart to pump sufficient blood

15. Figure 6-Illustration showing experimental set-up for performing isolated muscle contractions of an isolated muscle mass. Only 2 to 3 kg of muscle are active, and blood flow and oxygen uptake values in the region are incredibly high. This demonstrates that if blood flow is not limiting, extremely high values of oxygen uptake can be obtained. From reference 59 . Saltin, B. Hemodynamic adaptations to exercise. Am. J. Cardiol. 55:42D-47D, 1985 with permission.

16. Another way to look at blood flow is to realize the muscle has a tremendous capacity to accommodate blood flow
O2 uptake can reach ml/kg/min
Argues against skeletal muscle limitations to VO2max
When large muscle masses are utilized, blood flow is reduced and again VO2max is limited

17. What about VO2max adaptations?
What are the adaptations resulting in increased VO2max with training?
Primarily due to……?

18. Stroke Volume
TABLE 3. Physiological mechanisms behind the elevated ˙VO2max seen in elite endurance athletes, compared to normally active control subjects. Adapted from Rowell (58), p. 218.

19. What limits submaximal performance?

20. Figure 7-Relative contribution in percent of energy yield from aerobic and anaerobic processes, respectively, during maximal work of different durations. Drawn from data of reference 5 . Åstrand, P.-O. and K. Rodahl. Textbook of Work Physiology. New York: McGrawHill, 1970, pp

21. As exercise duration progresses, ATP needs are increasingly met by oxidative metabolism
VO2max-10 min- 70% aerobic
95% VO2max – 30 min – 90% aerobic
85% VO2max – 60 min – 95% aerobic
80 % VO2max – 120 min – 99% aerobic

22. Blood Lactate vs Duration
Figure 8-Blood lactate values of men after distance races of km. Broken line represents average resting value observed among runners in the laboratory. From reference 14 . Costill, D. L. Metabolic responses during distance running. J. Appl. Physiol. 28: , 1970 with permission.

23. Blood lactate accumulation is a reliable indicator of anaerobic metabolism
As exercise duration increases, blood lactate accumulation decreases

24. We know that VO2 is proportional to intensity
Figure 9-Linear relationship between running speed on the treadmill and oxygen uptake (mL·kg-1·min-1). Adapted from reference 10 . Bransford, D. R. and E. T. Howley. Oxygen cost of running in trained and untrained men and women. Med. Sci. Sports Exerc. 9:41-44, 1977.

25. And VO2max is a “good” predictor or performance in a heterogeneous population
Figure 10-Relationship between maximal oxygen consumption(˙VO2max) and distance running performance. Regression line represents the running times in a 10-mile test race. From reference 18 . Costill, D. L., H. Thomason, and E. Roberts. Fractional utilization of the aerobic capacity during distance running. Med. Sci. Sports Exerc. 5: , 1973 with permission.

26. Figure 11-Variability in the steady state oxygen uptake at fixed running speeds in 12 highly-trained and experienced male distance runners. From reference 13 . Conley, D. L. and G. Krahenbuhl. Running economy and distance running performance of highly trained athletes. Med. Sci. Sports Exerc. 12: , 1980.

27. Figure 12-Relationship between 10 km race time (y-axis) and steady-state oxygen uptake at 268 m·min-1 in 12 highly-trained and experienced male distance runners. From reference 13 . Conley, D. L. and G. Krahenbuhl. Running economy and distance running performance of highly trained athletes. Med. Sci. Sports Exerc. 12: , 1980.

28. So, VO2max will set your upper limit to utilize O2
This will determine your performance capacity
Factors such as economy and lactate threshold (which are trainable over time) will determine how good you will be relative to that capacity

29. Figure 13-Summary of the major variables related to˙VO2max and the maximum velocity that can be maintained in distance races.

31. Limiting factors for max oxygen uptake