OBJECTIVE: Examine the effects of exercise on femoral neck (FN) and lumbar spine (LS) bone mineral density (BMD) in premenopausal women. METHODS: Meta-analysis of randomized controlled exercise trials >= 24 weeks in premenopausal women. Standardized effect sizes (g) were calculated for each result and pooled using random-effects models, z score alpha values, 95% confidence intervals (CIs), and number needed to treat (NNT). Heterogeneity was examined using Q and I2. Moderator and predictor analyses using mixed-effects ANOVA and simple metaregression were conducted. Statistical significance was set at p <= 0.05. RESULTS: Statistically significant improvements were found for both FN (7 g's, 466 participants, g = 0.342, 95%CI 0.132 to 0.553, p = 0.001, Q = 10.8, p = 0.22, I2 = 25.7%, NNT 5) and LS (6 g's, 402 participants, g = 0.201, 95%CI 0.009 to 0.394, p = 0.04, Q = 3.3, p = 0.65, I2 = 0%, NNT 9) BMD. A trend for greater benefits in FN BMD was observed for studies published in countries other than the United States and for those who participated in home versus facility-based exercise. Statistically significant, or a trend for statistically significant, associations were observed for 7 different moderators and predictors, 6 for FN BMD and 1 for LS BMD. CONCLUSIONS: Exercise benefits FN and LS BMD in premenopausal women. The observed moderators and predictors deserve further investigation in well-designed randomized controlled trials.

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