ADDITIVE EFFECTS OF WEIGHT-BEARING EXERCISE AND ESTROGEN ON BONE-MINERAL DENSITY IN OLDER WOMEN

The separate and combined effects of weight-bearing exercise and hormo ne replacement therapy (HRT) on bone mineral density (BMD) were studie d in 32 women, 60 to 72 years of age, HRT consisted of continuous conj ugated estrogens 0.625 mg/day and trimonthly medroxyprogesterone aceta te 5 mg/day for 13 days. Exercise consisted of 2 months of low-intensi ty exercise followed by 9 months of more vigorous weight-bearing exerc ise similar to 45 minutes/day, greater than or equal to 3 days/week, a t 65-85% of maximal heart rate, Lumbar spine and proximal femur BMD we re significantly increased in response to exercise and to HRT, and tot al body BMD was significantly increased in response to HRT; neither ex ercise nor HRT had an effect on wrist BMD. The combination of exercise + HRT resulted in increased BMD at all sites except the wrist, with e ffects being additive for the lumbar spine and Ward's triangle and syn ergistic for the total body, Based on reductions in serum osteocalcin levels, it appears that increases in BMD in response to HRT and exerci se + HRT were due to decreased bone turnover, The lack of change in se rum osteocalcin and IGF-I in response to exercise alone suggests that increases in BMD were due to decreased bone resorption and not increas ed formation, Results indicate that weight-bearing exercise + HRT may be effective in preventing and/or treating osteoporosis, It is likely that the additive effects of weight-bearing exercise and HRT on bone m ineral accretion, coupled with other adaptations to the exercise (i.e. , increased strength and functional capacity), could effectively reduc e the incidence of falls and osteoporotic fractures.