Changes in mechanical properties and density of bone after exercise training

Changes in mechanical properties and desity of bone to deconditioning after exercise training were studied to fifty-four male rats. Mechanical tests were conducted for femur bone. The three-point bending test and stress relaxation test were performed with an Instron-type universal testing machine. Bone mineral content was measured by single photon absorptiometry at the middle site of the tibial, femur and humerus bones. The results are as follows:1) In the trained femur bone, fracture load, stiffness and deformation energy were greater than that in the control femur bone after 10weeks, 19weeks and 24weeks training period;2) Viscoelastic effect showed significant diffrences between the trained and the control femur bones;3) Density of femur and tibial bones showed significant diffrences between the trained and the control bones but also the humerus bone did diffrence tendency.