Quantifying the effects of acute hypoxic exposure on exercise performance and capacity: A systematic review and meta-regression

Objective: To quantify the effects of acute hypoxic exposure on exercise capacity and performance, which includes continuous and intermittent forms of exercise. Design: A systematic review was conducted with a three-level mixed effects meta-regression. The ratio of means method was used to evaluate main effects and moderators providing practical interpretations with percentage change. Data sources: A systemic search was performed using three databases (Google scholar, PubMed and SPORTDiscus). Eligibility criteria for selecting studies: Inclusion was restricted to investigations that assessed exercise performance (time trials (TTs), sprint and intermittent exercise tests) and capacity (time to exhaustion test, TTE) with acute hypoxic (<24 h) exposure and a normoxic comparator. Results: Eighty-two outcomes from 53 studies (N = 798) were included in this review. The results show an overall reduction in exercise performance/capacity −17.8 ± 3.9% (95% CI −22.8% to −11.0%), which was significantly moderated by −6.5 ± 0.9% per 1000 m altitude elevation (95% CI −8.2% to −4.8%) and oxygen saturation (−2.0 ± 0.4%; 95% CI −2.9% to −1.2%). TT (−16.2 ± 4.3%; 95% CI −22.9% to −9%) and TTE (−44.5 ± 6.9%; 95% CI −51.3% to −36.7%) elicited a negative effect, whilst indicating a quadratic relationship between hypoxic magnitude and both TTE and TT performance. Furthermore, exercise less than 2 min exhibited no ergolytic effect from acute hypoxia.