Impact of respiratory muscle training on exercise tolerance in hypobaric hypoxia: A pilot study in adult males

Hypoxia and certain chronic diseases can increase the work of breathing, potentially impacting the muscle hyperemic response during exercise and overall exercise performance. Respiratory muscle training (RMT) has been observed to decrease perceived effort under hypoxic conditions; however, it remains unclear if RMT affects exercise performance in acute hypoxia. We investigated whether 4 weeks of RMT could enhance submaximal and maximal exercise performance in hypoxia (barometric pressure = 425 mmHg, ~4876 m). Seven adult males underwent a 250 kJ submaximal (target RPE 15-17) cycling trial in hypoxia, followed by an incremental test to maximal exertion. After 4 weeks of RMT under normoxic conditions, these tests were repeated in hypoxia. After RMT, RPE showed no significant difference during the submaximal test (Pre-RMT: 16 ± 0.45, Post-RMT: 16 ± 0.45, p > 0.05) despite an increase in HR (Pre-RMT:154 ± 16, Post-RMT: 161 ± 12, p < 0.05). There were no significant differences in submaximal exercise performance. However, RMT did raise maximal oxygen uptake (V̇O₂max) peak power (Pre-RMT: 243 ± 35, Post-RMT: 252 ± 38 W, p = 0.04, Cohen's dz. = 0.97). Future investigations should explore the potential effects of RMT on perceived exertion and exercise tolerance at altitude. The results of this pilot study suggest that RMT may improve peak power at V̇O₂max, however given the limited sample size of this investigation, further research is required to determine if RMT impacts performance in other domains of exercise intensity. Furthermore, whether RMT impacts performance at altitude in females remains unknown.