End of exercise, end of benefits? A meta‐analysis of optimal physical exercise parameters for brain volume

Brain volume is closely linked to cognitive function, and its reduction is a key biomarker for neurodegenerative disease risk. Despite extensive research, uncertainties remain regarding the overall effects and optimal prescriptions of physical exercise on brain volume, as well as whether these changes translate into cognitive improvements. This preregistered systematic review and multilevel meta-analysis synthesized data from 59 randomized controlled trials (RCTs) involving 5099 participants. Physical exercise had a significant effect on brain volume (Hedges' g = 0.10), though the majority of effect sizes did not reach the minimal clinically important difference (MCID). Improvements that reached the MCID were observed among subgroups meeting World Health Organization (WHO) physical activity guidelines-particularly those practicing mind-body exercises, following "weekend warrior" patterns, or assessed at follow-up. Meta-regression revealed a significant association between exercise-induced brain volume changes and cognitive improvements (β = 0.20). These findings offer evidence-based guidance for optimizing interventions aimed at improving brain and cognitive health.