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 \(\left( {\dot V{\text{O}}_2 } \right)\) 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 \(\dot V{\text{O}}_2 \) may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean \(\dot V{\text{O}}_2 \max \) = 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% \(\dot V{\text{O}}_2 \max \) (Moderate1), 5 min cycling at 95% \(\dot V{\text{O}}_2 \max \) (Near Max) and then 6 min at 50% \(\dot V{\text{O}}_2 \max \) (Moderate2). In both series Near Max was performed in normoxia. \(\dot V{\text{O}}_2 \) 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 \(\dot V{\text{O}}_{2{\text{Moderate}}2} \) (+172±137 ml min−1 with [La] ~ 6 mmol l−1) compared to \(\dot V{\text{O}}_{2{\text{Moderate}}1} \) (+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 \(\dot V{\text{O}}_2 \) 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.