Influence of initial metabolic rate on the power-duration relationship for all-out exercise

A single 3-min all-out cycling test can be used to estimate the power asymptote (critical power, CP) and the curvature constant (W') of the power-duration relationship for severe-intensity exercise. It was hypothesized that when exercise immediately preceding the 3-min all-out test was performed < CP, the CP and W' parameters would be unaffected, whereas preceding exercise > CP would systematically reduce the W' without affecting the CP. Seven physically active males completed 3-min all-out cycling tests in randomized order immediately preceded by: unloaded cycling (control); 6-min moderate; 6-min heavy; 2-min severe (S2); or 4-min severe (S4) intensity exercise. The CP was estimated from the mean power output over the final 30 s of the test and the W' was estimated as the power-time integral above end-test power. There were no significant differences in the CP between control (279 +/- A 62), moderate (275 +/- A 52), heavy (286 +/- A 66 W), S2 (274 +/- A 55), or S4 (273 +/- A 65 W). The W' was significantly lower (P < 0.05) in S2 (11.5 +/- A 2.5) and S4 (8.9 +/- A 2.2) than in control (16.3 +/- A 2.3), moderate (17.2 +/- A 2.4) and heavy (15.6 +/- A 2.3 kJ). These results support the notion that the W' is predictably depleted only at a power output > CP whereas the CP is independent of the mechanisms which reduce W'.