This is a randomized cross-over comparison trial determining the effects of helium-hyperoxia on the performance of muscle specific one-legged cycling. Each participant will complete two constant power exercise tests while cycling with their right leg only. The tests will be separated by at least 24 h. The conditions of the two tests will be the same except that, in randomized order, the participant will breathe helium-hyperoxia (40% O2, 60% He) through a mask, or room air unencumbered by a mask with supplemental oxygen (4 L/min) provided by nasal cannula.
Participants will perform three exercise tests. First they will complete one incremental power exercise test using both legs (exercise capacity) in a standardized manner. Then they will complete two constant power (exercise endurance) cycle ergometer tests to the limit of tolerance (symptom based); the intent is to set an exercise level that comparable to the ideal training session that a patient would experience in the respiratory rehabilitation program. The same exercise regimen will be used in these two sessions except that the participant will breathe helium-hyperoxia (40% O2, 60% He) in one session and room air, with supplemental oxygen (4 L/min) provided by nasal cannula, in the other. During all exercise sessions, heart rate, SaO2, and Borg scale ratings of dyspnoea and leg fatigue will be monitored. For each exercise test, participants will adhere to their usual medical regimens, not eat for 2 h before the test and not drink caffeinated beverages for 2 h before the test. All tests will be separated by at least 24 h.
