Exercise intensity is associated with increased bone mineral density (BMD) and altered bone geometry. To determine the relationship between the intensity of exercise and bone adaptation, we measured BMD of the femur by dual-energy X-ray absorptiometry...
Exercise intensity is associated with increased bone mineral density (BMD) and altered bone geometry. To determine the relationship between the intensity of exercise and bone adaptation, we measured BMD of the femur by dual-energy X-ray absorptiometry (DXA), and bone geometry of tibia by histomorpometry, in 40 male Sprague-Dawley rats. A new resistance training apparatus that induces rats to perform motions analogous to human resistance training was designed for this study. Resistance training consisted of squatting at 40%(low intensity group; L-RE) and 75%(high intensity group; H-RE) of one repetition maximum (1RM) for 45~50 min/day and 3~4 days/week with a progressively increased load. After 8 week of training, total calf muscle weight and BMD of the exercise group were significantly greater than the sedentary group. However, no differences were found the between L-RE and H-RE in femur BMD. A significantly increased Tr.N of trabecullar bone was observed in the H-RE compared with the L-RE. Bone strength of L-RE was increased by resistance training, but no differences were in Tr.N and Tr.Th of tibia. These findings suggest that high-intensity has a direct effect on bone formation. This may contribute to the beneficial effect of exercise training models for humans in order to induce osteogenic response.