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The effects of a supervised 1-y walking program and increased dietary calcium (milk supplement, 831 mg/d, vs placebo drink, 41 mg/d) on bones were examined in 36 postmenopausal women (60.2 +/- 6.5 y). Trabecular bone-mineral density (BMD) of the lumbar spine (L1-L3), measured by computed tomography, increased by 0.5% in exercising women (n = 18) and decreased by 7.0% in sedentary women (n = 18; P = 0.02). Femoral-neck BMD measured by dual-photon absorptiometry (DPA) increased by 2.0% in women consuming high dietary calcium (n = 18) and decreased by 1.1% in those on moderate calcium intake (n = 18; P = 0.001). Neither exercise nor dietary calcium had an effect on lumbar spine (L2-L4) measured by DPA, distal radius measured by single-photon absorptiometry, or total body calcium measured by in vivo neutron activation. The varying proportions and rates of turnover of trabecular and cortical bone from one site to another suggest that exercise and high dietary calcium may preferentially alter bone density at different skeletal sites.

Habitual physical exercise has been reported to have beneficial effects on plasma lipoproteins. To examine this question in women, plasma cholesterol, triglyceride, and apolipoprotein (apo) A-I and B levels, and low density lipoprotein (LDL) particle size were determined in 25 women runners (9 of whom had exercise-related secondary amenorrhea) and 36 age-matched nonexercising women (controls). The eumenorrheic runners had significantly lower apo B levels and significantly greater mean apo A-I/apo B ratios and LDL particle sizes than did the control women (P less than 0.05). Lower apo B levels were correlated with decreased body mass index, a known exercise effect (P less than 0.0001). In addition, normally menstruating runners had cholesterol and triglyceride levels that were 7.6% and 25.4% lower, respectively, and apo A-I levels that were 6.4% higher than control women (P = NS). In amenorrheic runners all parameters were similar to values in control women, except that apo B levels were 20% lower (P less than 0.05). Amenorrheic runners had lower plasma apo A-I levels (13%) and significantly lower apo A-I/apo B ratios and estradiol levels than eumenorrheic runners, and serum estradiol values in the runners were correlated with apo A-I levels (P less than 0.01). These data indicate that the beneficial effects of strenuous exercise on plasma apo A-I levels and apo A-I/apo B ratios in women runners can be reversed by exercise-induced amenorrhea and decreased serum estradiol levels, and that women runners have lower apo B levels than nonexercising women, regardless of menstrual status.