High-intensity resistance training and postmenopausal bone loss: a meta-analysis

Introduction: Conflicting evidence exists regarding the optimum exercise for postmenopausal bone loss. A systematic review and meta-analysis was undertaken to evaluate the effects of randomised controlled trials (RCTs) of progressive, high-intensity resistance training on bone mineral density (BMD) amongst postmenopausal women. Methods: Structured electronic searching of multiple databases and hand-searching of key journals and reference lists was undertaken to locate relevant studies up to December 2004. Study quality and possible publication bias were assessed using recognised methods. Primary outcomes were absolute changes in BMD at the lumbar spine (LS), femoral neck (FN) and total hip (TH). A priori defined subgroup analyses included concurrent hormonal or antiresorptive therapy or calcium supplementation during the intervention. The weighted mean difference method (WMD) was used for combining study group estimates. Random or fixed effect models were applied according to study heterogeneity observed from the I-2 statistic. Results: At the LS, 14 RCT study groups were homogenous ( I-2= 25.2%) in demonstrating a significant increase ( P= 0.006) in BMD of 0.006 g/cm(2) ( fixed effect; 95% CI 0.002 - 0.011) following high-intensity resistance training. In contrast, marked heterogeneity ( I-2= 88.2%) was apparent within 11 RCT study groups evaluating FN. For this comparison, a random effects model showed a positive change in FN BMD of 0.010 g/cm(2) ( 95% CI - 0.002 to 0.021; P = 0.11). Subgroup analyses showed more anatomical variability of BMD responses to resistance training according to participants' hormone therapy use. Treatment effects for study groups increasing all participants' calcium intake showed significant positive BMD changes at TH ( P= 0.007). Methodological quality of all included studies was low, and a reporting bias towards studies with positive BMD outcomes was evident. Conclusions: These findings are relevant to the nonpharmacological treatment of postmenopausal bone loss.