KINETICS OF OXYGEN-UPTAKE FOR SUBMAXIMAL EXERCISE IN HYPEROXIA, NORMOXIA, AND HYPOXIA

This study evaluated the dynamic response of VO2 in 6 healthy men at t he onset and end of submaximal step changes in work late during a pseu dorandom binary sequence (PRBS) exercise test and during ramp incremen tal exercise to exhaustion while breathing three different gas mixture s. The fractional concentrations of inspired O-2 were 0.14, 0.21. and 0.70 for the hypoxic, normoxic, and hyperoxic tests, respectively. Bot h maximal VO2 and work rate was significantly reduced in hyperoxic tes ts compared to normoxic and hyperoxic rests. Maximal work rate was gre ater in hyperoxia than in normoxia. Work rate at ventilatory threshold was lower in hypoxia than in normoxia and hyperoxia but above the upp er limit of exercise for the submaximal tests. Hypoxia significantly s lowed the response of VO2 both at the onset and end of exercise compa, ed to normoxia and hyperoxia. Hypoxia also modified the response to P RBS exercise, and again there was no difference between normoxia and h yperoxia. These data support the concept that VO2 kinetics can be slow ed from the normoxic response by a hypoxic gas mixture.