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 remaining W´ (W´BAL) by modelling flat over-ground power during exhaustive intermittent running. Method Nine male participants completed a ramp test, 3-minute all-out test and the 30-15 intermittent fitness test (30-15 IFT), and performed a severe-intensity constant work-rate trial (SCWR) at the maximum oxygen uptake velocity (vV̇O2max). Four intermittent trials followed: 60-s at vV̇O2max +50% Δ1 (Δ1 = vV̇O2max – critical velocity [VCrit]) interspersed by 30-s in light (SL; 40% vV̇O2max), moderate (SM; 90% gas exchange threshold velocity [VGET]), heavy (SH; VGET +50% Δ2 [Δ2 = VCrit - VGET]) or severe (SS; vV̇O2max -50% Δ1) domains. Data from Global Positioning Systems were derived to model over-ground power. The difference between critical and recovery power (DCP), time constant for reconstitution of W´ (τ_(W^(´ ) )), time to limit of tolerance (TLIM), and W´BAL from the integral (W´BALint), differential (W´BALdiff) and locomotor-specific (OG-W´BAL) methods were compared. Results The relationship between τ_(W^(´ ) ) and DCP was exponential (r2 = 0.52). The τ_(W^(´ ) )for SL, SM and SH trials were 119 ± 32-s, 190 ± 45-s, and 336 ± 77-s, respectively. Actual TLIM in the 30-15 IFT (968 ± 117-s) compared closely to TLIM 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.