The constant work rate critical power protocol overestimates ramp incremental exercise performance

Purpose: The parameters of the power-duration relationship (i.e., the critical power, CP, and the curvature constant, W′) may theoretically predict maximal performance capability for exercise above the CP. The CP and Wʹ are associated with the parameters of oxygen uptake (V ˙ O2) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and Wʹ derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance. Methods: Thirty subjects (males, n = 28; females, n = 2) performed a ramp incremental test, and 3–5 CWR prediction trials for the determination of the CP and Wʹ. Multiple ramp incremental tests and corresponding CP and Wʹ estimates were available for some subjects such that in total 51 ramp test performances were predicted. Results: The ramp incremental test performance (729 ± 113 s) was overestimated by the CP and Wʹ estimates derived from the best (751 ± 114 s, P < 0.05) and worst (749 ± 111 s, P < 0.05) individual fits of CWR prediction trial data. The error in the prediction was inversely correlated with the magnitude of the Wʹ for the best (r = −0.56, P < 0.05) and worst individual fits (r = −0.36, P < 0.05). Conclusions: The overestimation of ramp incremental performance suggests that the CP and Wʹ derived from different work-rate forcing functions, thus resulting in different V ˙ O2 kinetics, cannot be used interchangeably. The present findings highlight a potential source of error in performance prediction that is of importance to both researchers and applied practitioners.