A 30-Min Rest Protocol Does Not Affect W', Critical Power, and Systemic Response.

Abstract

This study aimed to assess and compare the systemic response of oxygen uptake kinetics and muscle deoxygenation between a 30-min rest protocol and a multivisit protocol on the parameters of the power-duration relationship (i.e., critical power [CP] and W'). Nine endurance-trained triathletes reported to the laboratory on five occasions: a preliminary graded exercise test and a familiarization, a 30-min single-visit protocol (time trials of 10, 5, and 2 min in that order interspersed with 30 min rest), and a multivisit protocol (time trials of 10, 5, and 2 min in randomized order interspersed by >24 h rest). Heart rate (HR) was recorded continuously, respiratory gases were measured breath by breath, and deoxygenation was recorded at 10 Hz using near-infrared spectroscopy (NIRS) during all tests. Blood lactate (BLa-) concentration was measured before all time trials. Maximal HR (HRmax), oxygen uptake (V˙O2) during the first 2 min (V˙O2onset), mean response time, end-exercise V˙O2 (V˙O2peak), V˙O2 amplitude (amplV˙O2), O2 deficit, NIRS τ, amplitude (amplNIRS), and time delay were assessed. To compare the two protocols and to assess the differences in W' and CP, a paired sample t-test was used as well as a two-way ANOVA to assess the differences between trials and/or protocols, including trial-protocol interactions. No significant differences, and trivial effect sizes, were found for W' and CP between protocols (P = 0.106-0.114, d < 0.01-0.08). Furthermore, no significant differences between protocols were found for all parameters, except for [BLa-]. Significant differences between trials were found for V˙O2ampl, V˙O2onset, NIRS τ, amplNIRS, [BLa-], and HRmax. Results suggest that W' and CP can be determined using the 30-min rest protocol without confounding effects of previous severe exercise compared with the multivisit protocol.