Effects of low and high levels of moderate hypoxia on anaerobic energy release during supramaximal cycle exercise

The purpose of this study was to investigate whether hypoxia can alter anaerobic energy release during supramaximal exercise. Seven male subjects performed 12 submaximal cycling tests to establish the relationship between workload and O₂ demand. The subjects also performed 40 s Wingate tests (WT) under normoxia (room air), two levels of moderate hypoxia of 16.4% O₂ and 12.7% O₂. We measured the power output and oxygen uptake (VO₂) during each test and estimated the O₂ demand, O₂ deficit and percentage of anaerobic energy release (%AnAER). These data were analyzed for each 20 s interval. At all intervals, there were no differences in Pmean·body mass (BM)⁻¹, O₂ demand·BM⁻¹ or O₂ deficit·BM⁻¹ among the three O₂ conditions. However, under hypoxia of 12.7%, VO₂·BM⁻¹ was significantly decreased and %AnAER was significantly increased in the late phase (20–40 s) of the WT, compared to normoxia (P<0.05). There were no such significant differences between normoxia and hypoxia of 16.4%. Thus, the present results show that the degree of hypoxia affects the magnitude of the hypoxia-induced increase in anaerobic energy release in the late phase of the WT and suggest that certain degrees of hypoxia induce significant increases in the amount of anaerobic energy released, compared to normoxia.