Critical power testing or self-selected cycling: Which one is the best predictor of maximal metabolic steady-state?

Critical power (CP) demarcates the boundary between heavy and very heavy exercise intensity domains, and therefore, the power output (PO) that can be sustained at the maximal metabolic steady-state during constant-PO exercise (i.e., maximal lactate steady-state (MLSS)). However, the estimated CP does not always reflect a sustainable intensity of exercise, where blood lactate concentration ([La]) and oxygen uptake (V˙O₂) reach a plateau. Objectives To test cyclists’ ability to predict their highest PO associated with metabolic steady-state based on their own perception of effort. Design Repeated measures. Methods Thirteen healthy young cyclists (26 ± 3years; 69.0 ± 9.2 kg; 174 ± 10 cm) were tested. Five time-to-exhaustion trials were used to derive CP based on a 2-parameter hyperbolic model (CP_HYP). Participants performed two 30-min rides at a self-selected PO that they considered their highest sustainable exercise intensity (CP_SELF). Additionally, MLSS was determined as the highest PO at which variation in [La] ≤1.0 mmol L⁻¹ between the 10th and 30th min was observed during a 30-min ride. Results Mean PO at CP_SELF (233 ± 42 W) was similar (p > 0.05) to MLSS (233 ± 41 W), whereas CP_HYP (253 ± 44 W) consistently overestimated (p < 0.05) the PO associated to metabolic steady-state. The limits of agreement (LOA) between MLSS and CP_SELF were −20 to +20 W (bias = 0 W, p > 0.05), whereas the LOA between CP_HYP and CP_SELF were −40 to 0 W (bias = −20 W, p < 0.05). CP_SELF and MLSS presented similar (p > 0.05) metabolic response (i.e., V˙O₂, [La], and HR). Conclusions Compared to CP_HYP, CP_SELF may offer a more precise approach to predict the constant-PO associated with maximal physiological steady-state.