Effectiveness of hypoxic versus normoxic exercise on cardiovascular function in people without cardiovascular diseases: A systematic review and meta‐analysis

Background Exercise is a well‐known strategy for the prevention and treatment of cardiovascular diseases; however, the potential additional benefits of hypoxic exercise on cardiovascular function in comparison to normoxic exercise are still unknown. This study aimed to synthesize the hypoxic exercise protocols of application and to comparatively determine the effects of hypoxic versus normoxic exercise on cardiovascular function (i.e. haemoglobin concentrations, arterial oxygen saturation %, maximal heart rate, blood pressure at rest and blood lactate levels) in people without cardiovascular diseases. Methods We systematically searched five databases, from inception to September 2023, and selected randomized controlled trials (RCTs) comparing the effects of chronic hypoxic exercise versus normoxic exercise on cardiovascular function in people without cardiovascular diseases. A random effects meta‐analysis with both the Dersimonian‐Laird and the Hartung‐Knapp‐Sidik‐Jonkman methods was conducted to estimate the pooled standardized mean differences (SMDs) and their 95% confidence intervals (95% CIs) of the hypoxic exercise effectiveness on each of the included outcomes related to cardiovascular function. We performed meta‐regression models—considering total sample size, age, BMI, length of intervention and FiO 2 percentages—to determine their influence on the estimated effect. Subgroup analyses based on age, gender, type of exercise and health status of participants were conducted. Results A total of 31 RCTs involving 910 individuals were included. None of the pooled SMDs comparing hypoxic versus normoxic exercise were statistically significant. Subgroup analyses were only significant for lactate in people under 30 years of age and healthy and/or athletic individuals (.59; 95% CI .11, 1.06). Conclusions Our data suggest that there were no additive benefits of performing hypoxic exercise on the cardiovascular function parameters explored for up to 7 weeks when compared to normoxic exercise in people without cardiovascular disease, except for a moderate increase in blood lactate levels in young healthy and/or athletic individuals.