Experienced Cyclists Predict The Highest Sustainable Intensity Of Exercise More Effectively Than Critical Power Testing.

Abstract

Critical Power (CP) demarcates the boundary between sustainable and unsustainable exercise, and it is widely used as a measure of exercise tolerance/performance. Evaluation typically consists of a time-consuming and physically demanding protocol of 3-5 time-to-exhaustion trials (TTE) ranging from 1 to 20 min. However, the power output (PO) associated with the calculated CP does not always reflect a sustainable intensity of exercise, and lactate concentration ([La]) cannot be stabilized (i.e. lactate steady-state is not reached). PURPOSE: To test cyclists’ ability to predict their CP based on their own perception of effort, and to compare this PO with those derived from 5 TTE trials and maximal lactate steady-state (MLSS) measurements. METHODS: Seven experienced cyclists (28±3 yrs; 68.4±7.3 kg; 175±9 cm) participated in the study. A ramp incremental test to exhaustion was performed on a cycle ergometer (Velotron Dynafit Pro, Racer Mate, Seattle, WA, USA) for determination of VO2peak (Quark CPET, Cosmed, Rome, Italy) and peak PO (POpeak). PO of CP from 5 TTE trials was derived from a 2-parameter hyperbolic model (POHYP). Participants also performed two 30-min rides at a self-selected PO (POSELF) that they considered the highest intensity of exercise they could sustain for a prolonged time. Additionally, participants performed 30-min rides at the estimated POHYP for determination of PO at MLSS (POMLSS). [La] was measured at 5-min intervals and POMLSS was considered as the highest PO at which variation of [La] ≤ 1.0 mM·L-1 between the 10th and the 30th min. RESULTS: Mean VO2PEAK and POPEAK were 4.30±0.67 L·min-1 and 383±53 W, respectively. POHYP, POSELF and POMLSS were similar (267±39 W, 246±37 W and 246±37 W, respectively; p > 0.05). Bland-Altman plots were used to determine limits of agreement (LOA) between POSELF and POMLSS (-22 to 22 W, bias = 0; p > 0.05), POHYP and MLSS (-8 to 51 W, bias = 21; p > 0.05) and POSS and POHYP (-39 to -4 W, bias = -21 W; p > 0.05). Although POSELF and POHYP had similar magnitudes of range when compared to POMLSS, POHYP consistently over predicted POSELF and POMLSS. CONCLUSION: Experienced cyclists can predict their maximal sustainable PO for a prolonged time-trial with more precision than the current CP testing. This finding challenges the practical application of this test in experienced cyclists.