Associations of Laboratory- and Field- derived Measurements of Critical Power with W’-kinetics during 40-km Cycling Time Trial Performances

Abstract

International Journal of Exercise Science 18(8): 757-773, 2025. This study aimed to establish whether a laboratory (lab) based 3-minute all-out (3MT) protocol and a field-based 3MT protocol would yield similar peak power (Pmax), critical power (CP), and curvature constant (W’) profiles and the implications of parameter estimation for informing a 40-km time trial (TT) performance. Nine competitive male cyclists (mean ± SD: age 36.5 ± 10.42 y, mass = 80.5 ± 10.6 kg, height 1.8 ± 0.1 m) completed two 3MTs on separate days, as well as a 40-km time trial. Both lab and field-based protocols evoked similar CP (p = 0.160) and W′ (p = 0.200) profiles, but Pmax (p = 0.012) may be more sensitive to biomechanical disparities and testing environment. Strong positive associations were observed with W’-kinetics (r = 0.73) and W’ (r = 0.83) and moderate-to-strong negative associations with mean TT power (r = -0.75) and CP (r = -0.68). TT power outputs occur at 59-65% of CP, and finishing times appear to be informed by CP, W’ and Pmax with high degrees of accuracy (R2 \u3e 0.90). Although TT performances occur predominantly within the moderate-to-heavy intensity domains, the mean intensity from a cardiovascular and core temperature perspective was high (i.e., ~90% HRmax; ~39oC). TT performances appear to be accurately informed by CP, W’ and Pmax, with W’ dominating the predictive capacity associated with longer TT performances