Rate of utilization of a given fraction of W′ (the curvature constant of the power-duration relationship) does not affect fatigue during severe-intensity exercise

New Findings What is the central question of this study? Does the rate of utilization of W (the curvature constant of the power-duration relationship) affect fatigue during severe-intensity exercise? What is the main finding and its importance? The magnitude of fatigue after two severe-intensity exercises designed to deplete the same fraction of W (70%) at two different rates of utilization (fast versus slow) was similar after both exercises. Moreover, the magnitude of fatigue was related to critical power (CP), supporting the contention that CP is a key determinant in fatigue development during high-intensity exercise. Thus, the CP model is a suitable approach to investigate fatigue mechanisms during high-intensity exercise. The depletion of W (the curvature constant of the power-duration relationship) seems to contribute to fatigue during severe-intensity exercise. Therefore, the aim of this study was to determine the effect of a fast versus a slow rate of utilization of W on the occurrence of fatigue within the severe-intensity domain. Fifteen healthy male subjects performed tests to determine the critical power, W and peak torque in the control condition (T-CON) and immediately after two fatiguing work rates (THREE and TEN) set to deplete 70% W in either 3 (T-THREE) or 10min (T-TEN). The T-THREE and T-TEN were significantly reduced (F=19.68, P=0.01) in comparison to T-CON. However, the magnitude of reduction in peak torque (T-THREE=-19.8 +/- 10.1% versus T-TEN=-16.8 +/- 13.3%) was the same in the two fatiguing exercises (t=-0.76, P=0.46). There was a significant inverse relationship between the critical power and the reduction in peak torque during both THREE (r=-0.49, P=0.03) and TEN (r=-0.62, P=0.02). In contrast, the W was not significantly correlated with the reduction in peak torque during both THREE (r=-0.14, P=0.33) and TEN (r=-0.30, P=0.10). Thus, fatigue following severe-intensity exercises performed at different rates of utilization of W was similar when the same work was done above the critical power (i.e. same amount of W used).