Endurance exercise performance in acute hypoxia is influenced by expiratory flow limitation

Purpose We sought to determine if expiratory flow limitation influences intensive aerobic exercise performance in mild hypoxia. Methods Fourteen trained male cyclists were separated into flow-limited (FL, n = 7) and non-FL ( n = 7) groups based on the extent of expiratory flow limitation exhibited during maximal exercise in normoxia. Participants performed two self-paced 5-km cycling time trials, one in normoxic ( F I O 2 = 0.21) and one in mild hypoxic ( F I O 2 = 0.17) conditions in a randomized, balanced order with the subjects blinded to composition of the inspirate. Percent change from normoxia to hypoxia in average power output (%Δ P TT ) and time to completion (%Δ T TT ) were used to assess performance. Results Hypoxia resulted in a significant decline in estimated arterial O 2 saturation and decrements in performance in both groups, although FL had a significantly smaller %Δ P TT (−4.0 ± 0.5 vs. −9.0 ± 1.8 %) and %Δ T TT (1.3 ± 0.3 vs. 3.7 ± 0.9 %) compared to non-FL. At the 5th km of the time trial, minute ventilation did not change from normoxia to hypoxia in FL (3.4 ± 3.1 %) or non-FL (2.3 ± 3.7 %), but only the non-FL reported a significantly increased dyspnea rating in hypoxia compared to normoxia (~9 %). Non-FL athletes did not utilize their ventilatory reserve to defend arterial oxygen saturation in hypoxia, which may have been due to an increased measure of dyspnea in the hypoxic trial. Conclusion FL athletes experience less hypoxia-related aerobic exercise performance impairment as compared to non-FL athletes, despite having less ventilatory reserve.