Effects of priming exercise on V·O₂ kinetics and the power-duration relationship

Purpose: To investigate the influence of prior heavy- and severe-intensity exercise on the oxygen uptake (V·O2) kinetics and the power-duration relationship. Methods: Ten cyclists performed 13 exercise tests over a 4 week period, consisting of a ramp test to determine the gas exchange threshold (GET) and the peak V·O2, followed by a series of square-wave tests to exhaustion under three conditions: no prior exercise (control), prior heavy exercise (6 min at a work rate above GET but below critical power (CP)) and prior severe exercise (6 min at a work rate above the CP). Pulmonary gas exchange was measured throughout the exhaustive exercise bouts and the parameters of the power duration relationship (CP and the curvature constant, W) were determined from the linear work-time model. Results: Prior heavy exercise increased the amplitude of the primary V·O2 response (by ~0.19 ± 0.28 L·min-1, P = 0.001), reduced the slow component trajectory (by 0.04 ± 0.09 L·min-2; P = 0.002) and increased the time to exhaustion (by ~52 ± 92 s; P = 0.005). The CP was unchanged (control vs. prior heavy: 284 ± 47 vs. 283 ± 44 W; 95% CI, -7, 5 W) whereas the W was increased by heavy-intensity priming (16.0 ± 4.8 vs. 18.7 ± 4.8 kJ; 95% CI, 0.3, 5.2 kJ). Severe-intensity exercise had a similar effect on the V·O2 kinetics, but had no effect on the time to exhaustion, the CP (275 ± 45 W) or the W (16.7 ± 4.7 kJ). Conclusion: Prior heavy-intensity exercise primes the V·O2 kinetics and increases the amount of work that can be performed above the CP.