Exercise training in normobaric hypoxia in endurance runners. I. Improvement in aerobic performance capacity

  • Dufour S
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This study investigates whether a 6-wk intermittent hypoxia training (IHT), designed to avoid reductions in training loads and intensities, improves the endurance performance capacity of competitive distance runners. Eighteen athletes were randomly assigned to train in normoxia [Nor group; n = 9; maximal oxygen uptake ([IMG]f1.gif" ALT="V" BORDER="0">O2 max) = 61.5 {+/-} 1.1 ml{middle dot}kg-1{middle dot}min-1] or intermittently in hypoxia (Hyp group; n = 9; [IMG]f1.gif" ALT="V" BORDER="0">O2 max = 64.2 {+/-} 1.2 ml{middle dot}kg-1{middle dot}min-1). Into their usual normoxic training schedule, athletes included two weekly high-intensity (second ventilatory threshold) and moderate-duration (24-40 min) training sessions, performed either in normoxia [inspired O2 fraction (FIO2) = 20.9%] or in normobaric hypoxia (FIO2 = 14.5%). Before and after training, all athletes realized 1) a normoxic and hypoxic incremental test to determine [IMG]f1.gif" ALT="V" BORDER="0">O2 max and ventilatory thresholds (first and second ventilatory threshold), and 2) an all-out test at the pretraining minimal velocity eliciting [IMG]f1.gif" ALT="V" BORDER="0">O2 max to determine their time to exhaustion (Tlim) and the parameters of O2 uptake ([IMG]f1.gif" ALT="V" BORDER="0">O2) kinetics. Only the Hyp group significantly improved [IMG]f1.gif" ALT="V" BORDER="0">O2 max (+5% at both FIO2, P < 0.05), without changes in blood O2-carrying capacity. Moreover, Tlim lengthened in the Hyp group only (+35%, P < 0.001), without significant modifications of [IMG]f1.gif" ALT="V" BORDER="0">O2 kinetics. Despite similar training load, the Nor group displayed no such improvements, with unchanged [IMG]f1.gif" ALT="V" BORDER="0">O2 max (+1%, nonsignificant), Tlim (+10%, nonsignificant), and [IMG]f1.gif" ALT="V" BORDER="0">O2 kinetics. In addition, Tlim improvements in the Hyp group were not correlated with concomitant modifications of other parameters, including [IMG]f1.gif" ALT="V" BORDER="0">O2 max or [IMG]f1.gif" ALT="V" BORDER="0">O2 kinetics. The present IHT model, involving specific high-intensity and moderate-duration hypoxic sessions, may potentialize the metabolic stimuli of training in already trained athletes and elicit peripheral muscle adaptations, resulting in increased endurance performance capacity.

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  • S. P. Dufour

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