Do sex hormones influence the skeletal response to exercise?
In animal models, the effects of mechanical stress in the presence of estrogens (in females) or androgens (in males) on the bone proliferative response have been found to be either additive or synergistic (i.e., more than additive). There is also evidence for additive or synergistic effects of exercise and estrogens on BMD in women. In postmenopausal women, hormone therapy concurrent with exercise training had a greater beneficial effect on hip and spine BMD compared with exercise alone. There is some evidence that in postmenopausal women treated with hormone therapy, mixed loading exercise protocols, such as high-impact weight-bearing activities (e.g., jumping), combined with progressive-resistance training may have a greater benefit on BMD compared with single-mode exercise.
The responses of bone cells to mechanical stress involve activation of estrogen receptor alpha. Recent studies of laboratory animals suggest that estrogen receptor alpha may facilitate the effects of mechanical loading on bone whereas estrogen receptor beta may inhibit such effects. Additionally, the mechanical loading effects facilitated by estrogen receptor alpha signaling may be impaired in postmenopausal women because of reduced estrogen levels. However, the effects of age-related sex hormone deficiency on receptor density and/or function in bone remain unknown.