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Intensity-dependent tolerance to exercise after attaining V(O2) max in humans
Edward M Coats1, Harry B Rossiter, James R Day
1Department of Physiology, St George's Hospital Medical School, Cranmer Terrace, London, United Kingdom.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 1, 2003
Summary
High-intensity exercise capacity is limited by critical power (CP) and work capacity (W'). After exhaustion, exercise below CP is needed to replenish W', supporting aerobic energy transfer.
Area of Science:
- Exercise Physiology
- Sports Science
- Human Performance
Background:
- Tolerable duration of high-intensity exercise is linked to critical power (CP) and work capacity (W').
- It is hypothesized that exercise after exhaustion requires a work rate below CP for W' replenishment, utilizing aerobic energy transfer.
Purpose of the Study:
- To investigate if exercise performed below critical power (CP) allows for replenishment of work capacity (W') after exhaustion.
- To determine the influence of different work rates relative to CP and lactate threshold (theta(L)) on sustained exercise duration post-fatigue.
Main Methods:
- Six volunteers underwent ramp-incremental and constant-load cycle ergometry to determine CP, W', and VO2 max.
- Subjects performed exercise to exhaustion, followed by a reduction in work rate to 110% CP, 90% CP, or 80% theta(L) for a 20-minute target.
Main Results:
- Work capacity (W') averaged 20.9 kJ.
- Exercise at 110% CP was tolerated for only 30 seconds post-exhaustion.
- While 80% theta(L) was sustainable for 20 minutes, only two of six subjects completed 20 minutes at 90% CP, with others fatiguing prematurely.
Conclusions:
- The findings support the hypothesis that replenishing work capacity (W') after fatigue requires a work rate below critical power (CP).
- Variability in performance at 90% CP suggests factors like reduced CP post-exercise, altered lactate handling, or substrate depletion influence endurance.