Journal of Research in Medical Sciences1735-19953166202605201174311743EN20260519<p><strong>Background:</strong> Numerous epidemiological studies have identified a positive correlation between increased physical activity and raised levels of serum 25?hydroxyvitamin D (25(OH)D). However, it remains uncertain whether this correlation implies a  ause?and?effect relationship. The aim of this systematic review and meta?analysis was to analyze the effects of physical activity on serum 25(OH)D concentrations in humans.</p><p><strong>Materials and Methods:</strong> Interventional studies examining the effect of physical activity on serum 25(OH) D and published before July 2025 were detected by searching online databases, including PubMed, Embase, Scopus, and Web of Sciences, using a combination of suitable keywords. The heterogeneity among the included trials was evaluated using I2 statistics. Data were pooled using a random?effects model, and the weighted mean difference (WMD) was considered as the overall effect size.</p><p><strong> Results:</strong> Thirty eligible studies were included in the final analysis. Pooling effect sizes from studies demonstrated a significant increase in serum 25(OH)D levels following physical activity (WMD = 4.08 nmol/L; 95% confidence interval [CI]: 2.05, 6.11). Moreover, in subgroup analysis, the outdoor setting of the intervention resulted in a large and statistically significant difference in the serum Vitamin D levels, compared to the control groups (WMD: 17.23 nmol/L, 95% CI: 14.54, 19.92). However, the indoor setting of the physical activity intervention had a negligible effect on the serum Vitamin D levels (WMD: 0.37 nmol/L, 95% CI: ?0.38, 1.14), compared to the control groups.</p><p><strong> Conclusion:</strong> These results propose that prescribing outdoor physical activity may be an effective clinical strategy for improving Vitamin D levels, primarily mediated through sunlight exposure.</p>http://jrms.mui.ac.ir/index.php/jrms/article/view/11743http://jrms.mui.ac.ir/index.php/jrms/article/download/11743/6515