Aerobic exercise and bone density at the hip in postmenopausal women: A meta-analysis

Background. The effects of aerobic exercise on bone density at the hip in postmenopausal women in the absence of estrogen replacement therapy are not currently known. The purpose of this study was to examine the effects of aerobic exercise on bone density at the hip in postmenopausal women. Methods. Using the mete-analytic approach, studies dealing with the effects of aerobic exercise on bone density at the hip in postmenopausal women were searched for using computerized literature searches (MEDLINE, January 1978 to December 1995) as well as cross-referencing from retrieved review articles and original investigations. Results. A total of 18 effect sizes were derived from six studies. Using a fixed-effects model and bootstrap resampling (5,000 iterations) overall changes in bone density at the hip yielded an average effect size of 0.43 (95% CI = 0.04 to 0.81), equivalent to an overall change of approximately 2.42% (exercise = 2.13%; nonexercise = -0.29%). Statistically significant differences were observed when effect sizes were partitioned by country in which studies were conducted (United States, (x) over bar = 1.03, 95% CI = 0.48 to 1.68; other countries, (x) over bar = 0.18, 95% CI = -0.27 to 0.54; Q(b) = 5.44, P = 0.04) and calcium intake (greater than or equal to 1,000 mg/day, (x) over bar = 0.83, 95% CI = 0.49 to 1.23; <1,000 mg/day = -0.23, 95% CI = -0.85 to 0.21; Q(b) = 10.64, P = 0.002). Conclusions. The overall results of this study suggest that site-specific aerobic exercise has a moderately positive effect on bone density at the hip in postmenopausal women. However, a need exists for additional, well-designed studies before a final recommendation can be made regarding the efficacy of aerobic exercise as a nonpharmacologic intervention for optimizing bone density at the hip in postmenopausal women. (C) 1998 American Health Foundation and Academic Press.