A high blood lactate induced by heavy exercise does not affect the increase in submaximal VO sub(2) with hyperoxia

Few studies evidenced an enhancement in oxygen uptake ( VO sub(2)) during submaximal exercise in hyperoxia. This O sub(2) "overconsumption" seems to increase above the lactate threshold. The aim of this study was to determine whether the hyperoxia-induced enhancement in VO sub(2) may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean VO sub(2) max = 53.8 ml min super(-1) kg super(-1)) were randomized to two series of exercise in either normoxia or hyperoxia corresponding to an inspired O sub(2) fraction (F sub(l)O sub(2)) of 30%. Each series consisted of 6 min cycling at 50% VO sub(2) max (Moderate1), 5 min cycling at 95% VO sub(2) max (Near Max) and then 6 min at 50% VO sub(2) max (Moderate2). In both series Near Max was performed in normoxia. VO sub(2) was significantly greater under hyperoxia than in normoxia during Moderate1 (2192 plus or minus 189 vs. 2025 plus or minus 172 ml min super(-1)) and during Moderate2 (2352 plus or minus 173 vs. 2180 plus or minus 193 ml min super(-1)). However, the effect of the high F sub(l)O sub(2) was not significantly different on VO sub(2Moderate2) (+172 plus or minus 137 ml min super(-1) with [La] similar to 6 mmol l super(-1)) compared to VO sub(2Moderate1) (+166 plus or minus 133 ml min super(-1) with [La] similar to 2.4 mmol l super(-1)). [La] at the onset of Moderate2 was not different between normoxia and hyperoxia (10.1 plus or minus 2.2 vs. 10.9 plus or minus 1.6 mmol l super(-1)). The results show that VO sub(2) is significantly increased during moderate exercise in hyperoxia. But this O sub(2) 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 O sub(2) overconsumption with intensity during exercise in hyperoxia.