Bi-exponential modelling of [Formula: see text] reconstitution kinetics in trained cyclists.

PURPOSE: The aim of this study was to investigate the individual [Formula: see text] reconstitution kinetics of trained cyclists following repeated bouts of incremental ramp exercise, and to determine an optimal mathematical model to describe [Formula: see text] reconstitution. METHODS: Ten trained cyclists (age 41 ± 10 years; mass 73.4 ± 9.9 kg; [Formula: see text] 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. [Formula: see text] 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). RESULTS: A bi-exponential model outperformed the mono-exponential model of [Formula: see text] 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). CONCLUSIONS: W' 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.

Physiological and anthropometric determinants of critical power, W' and the reconstitution of W' in trained and untrained male cyclists.

PURPOSE: This study examined the relationship of physiological and anthropometric characteristics with parameters of the critical power (CP) model, and in particular the reconstitution of W' following successive bouts of maximal exercise, amongst trained and untrained cyclists. METHODS: Twenty male adults (trained nine; untrained 11; age 39 ± 15 year; mass 74.7 ± 8.7 kg; V̇O2max 58.0 ± 8.7 mL kg-1 min-1) completed three incremental ramps (20 W min-1) to exhaustion interspersed with 2-min recoveries. Pearson's correlation coefficients were used to assess relationships for W' reconstitution after the first recovery (W'rec1), the delta in W' reconstituted between recoveries (∆W'rec), CP and W'. RESULTS: CP was strongly related to V̇O2max for both trained (r = 0.82) and untrained participants (r = 0.71), whereas W' was related to V̇O2max when both groups were considered together (r = 0.54). W'rec1 was strongly related to V̇O2max for the trained (r = 0.81) but not untrained (r = 0.18); similarly, ∆W'rec was strongly related to V̇O2max (r = - 0.85) and CP (r = - 0.71) in the trained group only. CONCLUSIONS: Notable physiological relationships between parameters of aerobic fitness and the measurements of W' reconstitution were observed, which differed among groups. The amount of W' reconstitution and the maintenance of W' reconstitution that occurred with repeated bouts of maximal exercise were found to be related to key measures of aerobic fitness such as CP and V̇O2max. This data demonstrates that trained cyclists wishing to improve their rate of W' reconstitution following repeated efforts should focus training on improving key aspects of aerobic fitness such as V̇O2max and CP.

Slowing the Reconstitution of W' in Recovery With Repeated Bouts of Maximal Exercise.

PURPOSE: This study examined the partial reconstitution of the work capacity above critical power (W') following successive bouts of maximal exercise using a new repeated ramp test, against which the fit of an existing W' balance ( Wbal' ) prediction model was tested. METHODS: Twenty active adults, consisting of trained cyclists (n = 9; age 43 [15] y, V˙O2max 61.9 [8.5] mL·kg-1·min-1) and untrained cyclists (n = 11; age 36 [15] y, V˙O2max 52.4 [5.8] mL·kg-1·min-1) performed 2 tests 2 to 4 d apart, consisting of 3 incremental ramps (20 W·min-1) to exhaustion interspersed with 2-min recoveries. RESULTS: Intratrial differences between recoveries demonstrated significant reductions in the amount of W' reconstituted for the group and both subsets (P < .05). The observed minimal detectable changes of 475 J (first recovery) and 368 J (second recovery) can be used to monitor changes in the rate of W' reconstitution in individual trained cyclists. Intertrial relative reliability of W' reconstitution was evaluated by intraclass correlation coefficients for the group (≥.859) and the trained (≥.940) and untrained (≥.768) subsets. Absolute reliability was evaluated with typical error (TE) and coefficient of variation (CV) for the group (TE ≤ 559 J, CV ≤ 9.2%), trained (TE ≤ 301 J, CV ≤ 4.7%), and untrained (TE ≤ 720 J, CV ≤ 12.4%). CONCLUSIONS: The reconstitution of W' is subject to a fatiguing effect hitherto unaccounted for in Wbal' prediction models. Furthermore, the Wbal' model did not provide a good fit for the repeated ramp test, which itself proved to be a reliable test protocol.