The effects of differing resistance training modes on the preservation of bone mineral density in postmenopausal women: a meta-analysis

This meta-analysis synthesized current evidence from 24 clinical trials to evaluate the impact of different resistance training modes on postmenopausal bone loss. Exercise interventions were categorized into two training modes, namely resistance-alone versus combined resistance training protocols. The combined resistance training protocols were defined as the combination of resistance training and high-impact or weight-bearing exercise. The results suggested that the combined resistance training protocols were effective in improving bone mineral density (BMD) at the femoral neck and lumbar spine. Introduction The current meta-analysis aimed to examine the effects of combined resistance and resistance-alone training protocols on the preservation of femoral neck and lumbar spine BMD in postmenopausal women. Methods An electronic database search was conducted in PubMed, EMBASE, SPORTDiscus, Web of Science, and ProQuest up to March 1, 2014 for the influence of resistance exercise on BMD in postmenopausal women. The study quality was evaluated. The effect sizes were estimated in terms of the standardized mean difference (SMD). A subgroup analysis was conducted by exercise categories. Results Twenty-four studies were included in the overall analysis of skeletal response to resistance exercise. The between-study heterogeneity was evident for the hip (I (2) = 46.5 %) and spine (I (2) = 62.3 %). The overall analysis suggested that resistance training significantly increased femoral neck BMD (SMD = 0.303, 95 % confidence interval (95 % CI) = 0.127-0.479, p = 0.001) and lumbar spine BMD (SMD = 0.311, 95 % CI = 0.115-0.507, p = 0.002) in postmenopausal women. However, subgroup analysis indicated that combined resistance training programs significantly affected both the hip BMD (SMD = 0.411, 95 % CI = 0.176-0.645, p = 0.001) and spine BMD (SMD = 0.431, 95 % CI = 0.159-0.702, p = 0.002), whereas resistance-alone protocols only produced nonsignificant positive effects both on the femoral neck and lumbar spine BMD. Conclusions Combined resistance exercise protocols appear effective in preserving femoral neck and lumbar spine BMD in postmenopausal women, whereas resistance-alone protocols only produced a nonsignificant positive effect.