Exercise tolerance during flat over-ground intermittent running: modelling the expenditure and reconstitution kinetics of work done above critical power

PURPOSE: We compared a new locomotor-specific model to track the expenditure and reconstitution of work done above critical power (W´) and balance of W´ (W´(BAL)) by modelling flat over-ground power during exhaustive intermittent running. METHOD: Nine male participants completed a ramp test, 3-min all-out test and the 30–15 intermittent fitness test (30–15 IFT), and performed a severe-intensity constant work-rate trial (S(CWR)) at the maximum oxygen uptake velocity (vV̇O(2max)). Four intermittent trials followed: 60-s at vV̇O(2max) + 50% Δ(1) (Δ(1) = vV̇O(2max) − critical velocity [V(Crit)]) interspersed by 30-s in light (S(L); 40% vV̇O(2max)), moderate (S(M); 90% gas-exchange threshold velocity [V(GET)]), heavy (S(H); V(GET) + 50% Δ(2) [Δ(2) = V(Crit) − V(GET)]), or severe (S(S); vV̇O(2max) − 50% Δ(1)) domains. Data from Global Positioning Systems were derived to model over-ground power. The difference between critical and recovery power (D(CP)), time constant for reconstitution of W´ ([Formula: see text] ), time to limit of tolerance (T(LIM)), and W´(BAL) from the integral (W´(BALint)), differential (W´(BALdiff)), and locomotor-specific (OG-W´(BAL)) methods were compared. RESULTS: The relationship between [Formula: see text] and D(CP) was exponential (r(2) = 0.52). The [Formula: see text] for S(L), S(M), and S(H) trials were 119 ± 32-s, 190 ± 45-s, and 336 ± 77-s, respectively. Actual T(LIM) in the 30–15 IFT (968 ± 117-s) compared closely to T(LIM) predicted by OG-W´(BAL) (929 ± 94-s, P > 0.100) and W´(BALdiff) (938 ± 84-s, P > 0.100) but not to W´(BALint) (848 ± 91-s, P = 0.001). CONCLUSION: The OG-W´(BAL) accurately tracked W´ kinetics during intermittent running to exhaustion on flat surfaces.