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

Abstract

<p><b>Purpose</b> We compared a new locomotor-specific model to track the expenditure and reconstitution of work done above critical power (<i>W´</i>) and balance of <i>W´</i> (<i>W´</i>_BAL) by modelling flat over-ground power during exhaustive intermittent running.</p><p> <b>Method</b> 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 (<i>S</i>_CWR) at the maximum oxygen uptake velocity (<i>vV̇O</i>_2max). Four intermittent trials followed: 60-s at <i>vV̇O</i>_2max + 50% Δ1 (Δ1 = <i>vV̇O</i>_2max − critical velocity [<i>V</i>_Crit]) interspersed by 30-s in light (<i>S</i>_L; 40% <i>vV̇O</i>_2max), moderate (<i>S</i>_M; 90% gas-exchange threshold velocity [<i>V</i>_GET]), heavy (<i>S</i>_H; <i>V</i>_GET + 50% Δ2 [Δ2 = <i>V</i>Crit − <i>V</i>_GET]), or severe (<i>S</i>_S; <i>vV̇O</i>_2max − 50% Δ1) domains. Data from Global Positioning Systems were derived to model over-ground power. The difference between critical and recovery power (<i>D</i>_CP), time constant for reconstitution of <i>W´</i> (<i>τ</i>_<i>W′</i>), time to limit of tolerance (<i>T</i>_LIM), and <i>W´</i>_BAL from the integral (<i>W´</i>_BALint), differential (<i>W´</i>_BALdiff), and locomotor-specific (OG-<i>W´</i>_BAL) methods were compared.</p><p><b>Results</b> The relationship between <i>τ</i>_<i>W′</i> and <i>D</i>_CP was exponential (<i>r</i>2 = 0.52). The <i>τ</i>_<i>W′</i> for <i>S</i>_L, <i>S</i>_M, and <i>S</i>_H trials were 119 ± 32-s, 190 ± 45-s, and 336 ± 77-s, respectively. Actual <i>T</i>_LIM in the 30–15 IFT (968 ± 117-s) compared closely to <i>T</i>_LIM predicted by OG-<i>W´</i>_BAL (929 ± 94-s, <i>P</i> > 0.100) and <i>W´</i>_BALdiff (938 ± 84-s, </i>P</i> > 0.100) but not to <i>W´</i>_BALint (848 ± 91-s, <i>P</i> = 0.001).</p><p> <b>Conclusion</b> The OG-<i>W´</i>_BAL accurately tracked <i>W´</i> kinetics during intermittent running to exhaustion on flat surfaces.</p>