Endurance training and bone loss in calcium-deficient and ovariectomized rats.

We examined interactions among physical training, estrogen deficiency, and calcium deficiency with respect to the maintenance of femoral bone in five groups of 10 to 11-month-old female Fischer 344 rats: sedentary intact, sedentary ovariectomized, trained intact, trained ovariectomized, and control. All rats, except controls, were maintained on a calcium-deficient diet (0.02%) for 8 weeks, and had lower femoral weight, density, ash weight, and ash weight/volume than control rats. Ovariectomy combined with calcium deficiency decreased bone density more than did calcium deficiency alone. Treadmill training for 8 weeks resulted in an increase in maximal functional capacity, endurance time, heart weight and heart/body weight and attenuated the decrease in femoral density observed when ovariectomy and calcium deficiency both were present such that it was similar to that observed in calcium deficiency alone. We concluded that calcium-deficient ovariectomized rats undergo some of the bone changes characteristic of osteoporosis, and of these changes, a decrease in femoral density was attenuated by endurance training.