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

The aim of this study was to quantify the effects of acute hypoxic exposure on exercise capacity and performance, which includes continuous and intermittent forms of exercise. 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. A systemic search was performed using 3 databases (Google scholar, PubMed and SPORTDiscus). Inclusion was restricted to investigations that assessed exercise performance (time trials, sprint, and intermittent exercise tests) and capacity (time to exhaustion test (TTE)) with acute hypoxic ( < 24 hrs) exposure and a normoxic comparator. 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%). Time trial (-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 < 2-min exhibited no ergolytic effect from acute hypoxia. This review highlights the ergolytic effect of acute hypoxic exposure, which is curvilinear for TTE and TT performance with increasing hypoxic levels, but short-duration intermittent and sprint exercise seem to be unaffected