Exercise and regional bone mineral density in postmenopausal women: a meta-analytic review of randomized trials

By using the meta-analytic approach, the purpose of this study was to examine the effects of exercise on regional bone mineral density in postmenopausal women. A total of 11 randomized trials yielding 40 outcome measures and a total of 719 subjects (370 exercise, 349 nonexercise) met the criteria for inclusion: (1) randomized trials; (2) exercise as a primary intervention in postmenopausal women; (3) changes in regional bone mineral density reported; (4) comparative nonexercise group included; (5) studies published in English-language journals between January 1975 and December 1995. Across all designs and categories, treatment effect changes in bone density, weighted by sample size, ranged from -17.10 to 17.30% (mean, 0.27%; 95% confidence interval, 0.16-0.37%). When analyzed separately, sample weighted decreases of approximately -0.51 and -0.86% were found for exercise and nonexercise groups, respectively. Larger effects were observed when groups that did not measure bone density specific to the site loaded and groups that received some type of supplementation (calcium or hormone replacement therapy) were deleted from the model (mean change, 0.76%; 95% confidence interval, 0.6-0.93). Both aerobic and strength training enhanced regional bone mineral density (mean change: aerobic, 1.62% and 95% confidence interval, 1.12-2.12; strength, 0.65% and 95% confidence interval, 0.48-0.83). In conclusion, meta-analytic review of included studies suggests that exercise may slow the rate of bone loss in postmenopausal women. However, it is premature to form strong conclusions regarding the effects of exercise on regional bone mineral density in postmenopausal women. A need exists for additional, well designed studies on this topic before a recommendation can be made regarding the efficacy of exercise as a nonpharmacologic therapy for maintaining and/or increasing regional bone mineral density in postmenopausal women.