Residual Fatigue Does Not Affect Critical Power And w´ Using A Single-visit Protocol

Abstract

Traditionally, determining critical power (CP) and its related work above CP (W´) requires exhaustive constant-power trials interspersed by at least 24 h rest. During the last decade several approaches were undertaken to make the protocol less time consuming and to use self-paced ecological time-trials (TT). However, it is debateable whether residual fatigue induced by a single-visit protocol might affect CP and/or W´. Parameters of oxygen uptake (VO2) kinetics and muscle deoxygenation can be suggested as suitable to assess the effects of residual fatigue. PURPOSE: Assessing fatigue-related parameters of VO2 kinetics and muscle deoxygenation between a single-visit and a multi-visit protocol. METHODS: Nine well-trained male triathletes (mean ± SD; age: 27.7 ± 4.3 yrs; body mass: 75.6 ± 5.6 kg; VO2peak: 60.0 ± 6.5 mL/min/kg) participated. Athletes had to perform a single-visit (2, 5 and 10 min TT, interspersed by 30 min passive rest) as well as a multi-visit determination of CP and W´ (2, 5 and 10 min TT, interspersed by at least 24 h rest). During all tests, 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). The following parameters were assessed: maximal HR, VO2 during the first 2 min (VO2onset), mean response time (MRT), end-exercise VO2 (VO2peak), VO2 amplitude (amplVO2), O2 deficit, NIRS τ, amplitude (amplNIRS), and time-delay (TD). To compare the two protocols a paired sample t-test was used to assess the differences in CP and W´ and a two-way ANOVA to assess the differences between trials and/or groups as well as and trials x groups interactions. RESULTS: No significant differences were found for CP or W´ between protocols (p > 0.05). Significant main effects between trials were found for HR, VO2onset, amplVO2, τ and amplNIRS (p < 0.001), but not for MRT, VO2peak, O2 deficit and TD (p > 0.05). A post-hoc analysis of main effects did not reveal significant differences between corresponding trials (p > 0.05). CONCLUSIONS: Due to non-significant differences in fatigue-related parameters results indicate that the determination of CP and W´ using a single-visit protocol is not affected by residual fatigue. Consequently, the single-visit TT approach is a valid method to accurately determine CP and W´.