Effects of swimming and running trainings on mechanical properties of bone and bone density were investigated. Mechanical tests were conducted for tibial bone. The dynamic stiffness and tan δ were measured by a viscoelastic spectrometer. The three‐point bending test was performed with an Instron‐type universal testing machine. Bone mineral content was measured by photon absorptimetry at the middle site of the tibial bone. In the swimming case the stiffness and tan δ were, in average, larger for the trained rats than for the controlled group. The strength and the bone density were also larger for the trained group. In the running case, the negative effects were observed on these variables.