A high blood lactate induced by heavy exercise does not affect the increase in submaximal dot V{text{O}}_2 with hyperoxia

Few studies evidenced an enhancement in oxygen uptake during submaximal exercise in hyperoxia. This O₂ overconsumption seems to increase above the lactate threshold. The aim of this study was to determine whether the hyperoxia-induced enhancement in may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean = 53.8 ml min^–1 kg^–1) were randomized to two series of exercise in either normoxia or hyperoxia corresponding to an inspired O₂ fraction (F_IO₂) of 30%. Each series consisted of 6 min cycling at 50% (Moderate1), 5 min cycling at 95% (Near Max) and then 6 min at 50% (Moderate2). In both series Near Max was performed in normoxia. was significantly greater under hyperoxia than in normoxia during Moderate1 (2192±189 vs. 2025±172 ml min^–1) and during Moderate2 (2352±173 vs. 2180±193 ml min^–1). However, the effect of the high F_IO₂ was not significantly different on (+172±137 ml min^–1 with [La] ~ 6 mmol l^–1) compared to (+166±133 ml min^–1 with [La] ~ 2.4 mmol l^–1). [La] at the onset of Moderate2 was not different between normoxia and hyperoxia (10.1±2.2 vs. 10.9±1.6 mmol l^–1). The results show that is significantly increased during moderate exercise in hyperoxia. But this O₂ overconsumption was not modified by a high [La] induced by a prior heavy exercise. It could be concluded that lactate accumulation is not directly responsible for the increase in O₂ overconsumption with intensity during exercise in hyperoxia.The authors declare that the experiments comply with the current French laws.