A meta-analysis of impact exercise on postmenopausal bone loss: the case for mixed loading exercise programmes

OBJECTIVES: To assess the effects of differing impact exercise protocols on postmenopausal bone loss at the hip and spine. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Electronic bibliographic databases, key journals and reference lists of reviews and articles. REVIEW METHODS: Two independent reviewers assessed controlled trials evaluating effects of impact exercise on lumbar spine, femoral neck and total hip bone mineral density (BMD) in postmenopausal women for inclusion. Heterogeneity amongst trials and publication bias were assessed. Trial quality assessment was also performed. RESULTS: Impact protocols that included jogging mixed with walking and stair climbing, and protocols that incorporated impact exercise with high-magnitude loading (resistance exercises), were effective at lumbar spine (weighted mean difference (random effects) 0.025 g/cm(2) 95% CI (0.004 to 0.046) and 0.016 g/cm(2) 95% CI (0.005 to 0.027); p = 0.02 and p = 0.005 respectively), although heterogeneity was evident (I(2) = 88% and I(2) = 73%, where I(2) measures the extent of inconsistency among the trials). Effects on femoral neck BMD following these types of protocols were significant (weighted mean difference (fixed effect) 0.022 g/cm(2) 95% CI (0.014 to 0.030); p<0.001 and 0.005 g/cm(2) 95% CI (0.001 to 0.010); p = 0.03 respectively). High-impact only and odd-impact only protocols were ineffective in increasing BMD at any site. CONCLUSION: Mixed loading exercise programmes combining jogging with other low-impact loading activity and programmes mixing impact activity with high-magnitude exercise as resistance training appear effective in reducing postmenopausal bone loss at the hip and spine. Other forms of impact exercise appear less effective at preserving BMD in this population. However, diverse methodological and reporting discrepancies are evident in current published trials.