EFFECTS OF EXERCISE AT DIFFERENT AGES ON BONE-DENSITY AND MECHANICAL-PROPERTIES OF FEMORAL BONE OF AGED MICE

We determined the bone density and mechanical properties of bone speci mens from 5 groups of aged mice which had been subjected to voluntary exercise at different ages. ICR 10-week-old female mice were divided i nto control (C), and exercise-trained during age periods of 10-70 week s (EE), 10-30 weeks (GPE), 30-50 weeks (MPE) and 50-70 weeks (APE). It was found that in the exercise-trained groups body weight gain was su ppressed during the exercise-training period, and that de-training acc elerated weight gain. Bone density was significantly higher in all the exercise-trained groups than in the C group and cortical thickness in dex (CTI) was higher in the exercise-trained groups, except for the AP E group. Maximum breaking force, ultimate stress and elasticity in the exercise-trained groups were higher than in the C group except for th e APE group, whereas deformation in the APE group had a tendency to be higher than in the other groups. Blood C-terminal parathyroid hormone , calcitonin and calcium concentrations were similar among every group , but phosphorus concentrations tended to be higher in the exercise-tr ained groups than in the C group. These observations suggest that exer cise-training at every age suppresses age-associated bone loss: and th at the effect of exercise during youth is greater than that during old age. The results of this study suggest that the effect of exercise on bone at an older age is different from that at other ages.