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

Abstract

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±9.2kg; 174±10cm) 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] ≤1.0mmolL^-1 between the 10th and 30th min was observed during a 30-min ride.

Results: Mean PO at CP_SELF (233±42W) was similar (p>0.05) to MLSS (233±41W), whereas CP_HYP (253±44W) 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 +20W (bias=0W, p>0.05), whereas the LOA between CP_HYP and CP_SELF were -40 to 0W (bias=-20W, 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.

Keywords: Exercise intensity thresholds; Maximal lactate steady-state; Perceived exertion; Power-time relationship.