Maximal Oxygen Uptake Is Achievedin Hypoxia but Not Normoxia during an Exhaustive Severe Intensity Run

Highly aerobically trained individuals are unable to achieve maximal oxygen uptake (V˙ O2max) during exhaustive running lasting ∼2 min, instead V˙ O2 plateaus below V˙ O2max after ∼1 min. Hypoxia offers the opportunity to study the (V˙ O2) response to an exhaustive run relative to a hypoxia induced reduction in V˙ O2max. The aim of this study was to explore whether there is a difference in the percentage of V˙ O2max achieved (during a 2min exhaustive run) in normoxia and hypoxia. Fourteen competitive middle distance runners (normoxic V˙ O2max 67.0 ± 5.2 ml.kg−1.min−1) completed exhaustive treadmill ramp tests and constant work rate (CWR) tests in normoxia and hypoxia (FiO2 0.13). The V˙ O2 data from the CWR tests were modeled using a single exponential function. End exercise normoxic CWR V˙ O2 was less than normoxic V˙ O2max (86 ± 6% ramp, P < 0.001). During the hypoxic CWR test, hypoxic V˙ O2max was achieved (102 ± 8% ramp, P = 0.490). The phase II time constant was greater in hypoxia (12.7 ± 2.8 s) relative to normoxia (10.4 ± 2.6 s) (P = 0.029). The results demonstrate that highly aerobically trained individuals cannot achieve V˙ O2max during exhaustive severe intensity treadmill running in normoxia, but can achieve the lower V˙ O2max in hypoxia despite a slightly slower V˙ O2 response.