Abstract
Background: We measured exercise performance, gas-exchange and tissue oxygenation in healthy non-athletes undergoing cycle cardiopulmonary exercise test while breathing different oxygen concentrations.
Methods: 34 healthy (43±14y,14 women) performed 4 bicycle exercise tests to exhaustion on separate days with tests a) and b) using a progressive ramp protocol breathing FiO2 0.21 and 0.50, respectively, tests c) and d) a constant load exercise (75%Wmax) breathing FiO2 0.21, and 0.50, respectively, according to a single blinded randomized cross-over design. ECG, pulmonary gas exchange, pulse oximetry, brain- and muscle tissue oxygenation by NIRS were monitored breath by breath and variables averaged over 30 sec at rest and end-exercise.
Results: During maximal ramp exercise, hyperoxia was associated with a significantly higher work-rate (270±80 Wattvs.257±76,p=.000) , arterial- and brain-tissue-oxygenation (98.8±0.5vs.94.7±3.3,p=.000 and 67.5±9.0vs.61.1±11.1%, p=0.011) along with a lower brain-tissue-desaturation from rest to exercise (2.2±6.9vs.5.6±7.1%,p=.027) and borg-score (4.8±2.2vs.5.7±2.5,p=.010) whereas heart rate, minute ventilation and muscle-tissue oxygenation were unchanged. In submaximal constant load exercise hyperoxia significantly prolonged exercise time (16:48±0:07vs.11:04±0:05,p=.000) with lower minute ventilation, higher arterial- and muscle oxygenation but unchanged heart rate, brain-tissue oxygenation and borg scale.
Conclusion: Hyperoxia increases maximal work rate and submaximal endurance in healthy subjects. This is related to hyperoxia-associated increase in arterial and brain-tissue oxygenation under maximal exercise and muscle tissue-oxygenation under constant exercise.
- © 2014 ERS