Effects of swimming and weight loading on bone density and mechanical properties of the mouse femoral bone.

Effects of swimming and weight loading on femoral bone density and mechanical properties of the bone were investigated. ICR 8-week old female mice were divided into a swimming, weight-loading and control groups consisting 10 mice in each group. All mice were fed a standard diet and waterad libitum during the entire experiment. Body weight was significantly lower in the swimming group (p < 0.05) and the weight-loading group (p < 0.05) than in the control group, when the mean values were compared. The level of bone density was significantly higher (p < 0.05) in the weight-loading group than in the control group. As for the mechanical properties of the femur, there were no significant differences in the level of maximum breaking force, ultimate stress and elasticity between both the exercise groups and the control. Deformation, however, was significantly higher in both the exercise groups than in the control group. No significant difference in serum calcitonin was found between both the exercise groups and the control group. However, parathyroid hormone level had a tendency to be higher in the weigbt-loading group than in the control group. These results suggest that the effect of exercise on bone was stronger in weight loading than in swimming. Key words: Swimming, Weight loading, Bone density, Mechanical properties of bone, Mice.