Effects of acute hypoxia on ventilatory response at the onset of cycle exercise in man

In order to examine whether or not there are initial changes in ventilation at the start of bicycle exercise having work loads of differing intensities are affected with regard to normoxia and to hypoxia accompanying hypocapnia, six healthy male subjects performed submaximal exercise of 30 and 120 W at 60 rpm under normoxic (FIO2 = 0.21) and hypoxic (FIO2 = 0.11) conditions. Resting ventilation was significantly higher in hypoxia than in normoxia. However, no statistically significant differences in the initial change in ventilation at the start of exercise (delta VI assessed breath-by-breath) were found between eucapnic normoxia and hypocapnic hypoxia in both 30 and 120 W exercise. Moreover, blood lactate after exercise did not increase in any conditions as compared with rest. These observations suggest that the neurogenic ventilatory response immediately after submaximal exercise at a work load below the subject's anaerobic threshold is independent from PO2.