The effects of hypoxic versus normoxic exercise training on body composition, cardiometabolic health markers, and functional performance in adults: a systematic review and meta-analysis

Exercise training under hypoxia (HET) has recently gained attention and theoretically has beneficial synergistic effects on body composition, cardiometabolic health, and functional performance compared with exercise training under normoxia (NET). Findings are, however, mixed, so the present study aimed to investigate the potential superiority of HET over NET. A comprehensive search was conducted in three primary databases, i.e., PubMed, Scopus, and Web of Science, from inception to May 2024 to identify original studies that compared the effects of HET versus NET on body composition, lipid profiles, glycemic markers, blood pressures, inflammatory markers, muscular strength, and VO2max. Weighted mean differences (WMD) or standardized mean differences (SMD), along with 95% confidence intervals (CIs), were calculated using random effects models. A total of 43 studies involving 1,154 participants with mean ages ranging from ~ 21 to 82 years were included in the meta-analysis. Overall, HET decreased body fat and circulating triglycerides (TG) while improving both absolute and relative VO₂max significantly more than NET. There were, however, no significant differences for any other outcomes, whilst age, BMI, health status, and exercise mode had no moderating effects. HET provides a small but statistically significant benefit for body fat, TG, and a meaningful improvement in VO2max as compared with NET. Longer-term interventions are now needed to confirm the effectiveness of HET for these and other health outcomes.