Effects of exercise training on bone remodeling, insulin-like growth factors, and bone mineral density in postmenopausal women with and without hormone replacement therapy

The purpose of this study was to determine the effects of 12 months of weight bearing and resistance exercise on bone mineral density (BMD) and bone remodeling (bone formation and bone resorption) in 2 groups of postmenopausal women either with or without hormone replacement therapy (HRT). Secondary aims were to characterize the changes in insulin-like growth factors-1 and -2 (IGF-1 and -2) and IGF binding protein 3 (IGFBP3) in response to exercise training. Women who were 3-10 years postmenopausal (aged 4065 years) were included in the study. Women in the HRT and no HRT groups were randomized into the exercise intervention, resulting in four groups: (1) women not taking HRT, not exercising; (2) those taking HRT, not exercising; (3) those exercising, not taking HRT; and (4) women exercising, taking HRT. The number of subjects per group after 1 year was 27, 21, 25, and 17, respectively. HRT increased BMD at most sites whereas the combination of exercise and HRT produced increases in BMD greater than either treatment alone. Exercise training alone resulted in modest site-specific increases in BMD. Bone remodeling was suppressed in the groups taking HRT regardless of exercise status. The bone remodeling response to exercise training in women not taking HRT was not significantly different from those not exercising. However, the direction of change suggests an elevation in bone remodeling in response to exercise training, a phenomenon usually associated with bone loss. No training-induced differences in IGF-1, IGF-2, IGF-1:IGF-2 (IGF-1: IGF-2), and IGFBP3 were detected.