Abstract
PurposeThe aim of this study was to investigate the individual W^{^{prime}} reconstitution kinetics of trained cyclists following repeated bouts of incremental ramp exercise, and to determine an optimal mathematical model to describe W^{^{prime}} reconstitution.MethodsTen trained cyclists (age 41 ± 10 years; mass 73.4 ± 9.9 kg; dot{V}{text{O}}_{2max } 58.6 ± 7.1 mL kg min−1) completed three incremental ramps (20 W min−1) to the limit of tolerance with varying recovery durations (15–360 s) on 5–9 occasions. W^{^{prime}} reconstitution was measured following the first and second recovery periods against which mono-exponential and bi-exponential models were compared with adjusted R2 and bias-corrected Akaike information criterion (AICc).ResultsA bi-exponential model outperformed the mono-exponential model of W^{^{prime}} reconstitution (AICc 30.2 versus 72.2), fitting group mean data well (adjR2 = 0.999) for the first recovery when optimised with parameters of fast component (FC) amplitude = 50.67%; slow component (SC) amplitude = 49.33%; time constant (τ)FC = 21.5 s; τSC = 388 s. Following the second recovery, W′ reconstitution reduced by 9.1 ± 7.3%, at 180 s and 8.2 ± 9.8% at 240 s resulting in an increase in the modelled τSC to 716 s with τFC unchanged. Individual bi-exponential models also fit well (adjR2 = 0.978 ± 0.017) with large individual parameter variations (FC amplitude 47.7 ± 17.8%; first recovery: (τ)FC = 22.0 ± 11.8 s; (τ)SC = 377 ± 100 s; second recovery: (τ)FC = 16.3.0 ± 6.6 s; (τ)SC = 549 ± 226 s).ConclusionsW′ reconstitution kinetics were best described by a bi-exponential model consisting of distinct fast and slow phases. The amplitudes of the FC and SC remained unchanged with repeated bouts, with a slowing of W′ reconstitution confined to an increase in the time constant of the slow component.
Highlights
The critical power model introduced by Monod and Scherrer (1965) describes the hyperbolic relationship between constant power output and tolerable duration within the confines of the ‘severe’ intensity domain (Eq 1)
The kinetics of W′ are of particular interest within competitive cycle sport as the outcomes of many races are decided by the efficacy of riders’ intermittent efforts above critical power (CP) interspersed with short recovery periods below CP (Craig and Norton 2001; Vogt et al 2007) that allow for the partial reconstitution of W′ (Chidnok et al 2013a)
A priori paired sample t tests were used to compare the means of W′ reconstitution at each time point from the first and second recovery periods, together with effect sizes (ES) calculated as the difference between the means divided by the pooled SD
Summary
The critical power model introduced by Monod and Scherrer (1965) describes the hyperbolic relationship between constant power output and tolerable duration within the confines of the ‘severe’ intensity domain (Eq 1). Where Tlim is the time to limit of tolerance (s); W′ is the work capacity above CP (J); P is the power output (W); CP is the critical power (W); S is the ramp rate (W s−1). CP represents the highest power output that can be sustained by the provision of adenosine triphosphate from wholly aerobic means (Coats et al 2003; Poole et al 1988), and the maximum work rate at which metabolic homeostasis can be maintained. As such, it denotes the physiological boundary between the ‘heavy’ and ‘severe’ intensity domains (Jones et al 2019). The kinetics of W′ are of particular interest within competitive cycle sport as the outcomes of many races are decided by the efficacy of riders’ intermittent efforts above CP interspersed with short recovery periods below CP (Craig and Norton 2001; Vogt et al 2007) that allow for the partial reconstitution of W′ (Chidnok et al 2013a)
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