Effects of jump training on bone hypertrophy in young and old rats.

The effects of jump training on bone hypertrophy were investigated in 3, 6, 12, 20 and 27 month-old female Fischer 344 rats. The rats of all age groups were divided into jump training (height: 40 cm, 100 times/day, 5 days/wk for 8 wk), run training (speed: 30 ml/min, 1 h/day, 5 days/wk for 8 wk) or sedentary group. Fat-free dry weights (FFW) of the femur and the tibia were significantly greater in the jump-trained rats than in the run-trained rats, and were significantly greater in the run-trained rats than in the sedentary rats. Jump training significantly increased FFW of the femur and the tibia not only in young rats but also in old rats, while run training did not increase FFW significantly in old rats. In young rats, both jump training and run training significantly increased the length of the femur and the tibia and the diameter of the femur. The diameter of the tibia was greater in the jump-trained rats than in the sedentary and the run-trained rats in all age groups. The results of the present study indicate that jump training was a more effective training mode than run training for bone hypertrophy and that the effects were not limited by age.