A high blood lactate induced by heavy exercise does not affect the increase in submaximalwith hyperoxia.

Few studies evidenced an enhancement in oxygen uptakeduring 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 inmay 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 (FIO2) 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 FIO2 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 thatis 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. [ABSTRACT FROM AUTHOR]