Effects of tower climbing exercise on bone mass, strength, and turnover ingrowing rats

To determine the effects of tower climbing exercise on mass, strength, and local turnover of bone, 50 Sprague-Dawley rats, 10 weeks of age, were assig ned to five groups: a baseline control and two groups of sedentary and exer cise rats. Rats voluntarily climbed the 200-cm tower to drink water from th e bottle set at the top of it. In 4 weeks, the trabecular bone formation ra te (BFR/bone surface [BSI), bone volume (BV/TV), and trabecular thickness ( Tb.Th) of both the lumbar vertebra and tibia and the bone mineral density ( BMD) of the tibia increased, while the osteoclast surface (Oc.S) decreased. The parameter values in the midfemur, such as the total cross-sectional ar ea, the moment of inertia, the periosteal mineralizing surface (MS/BS), min eral apposition rate (MAR), BFR/BS, and bending load increased, while the e ndosteal MAR decreased. In 8 weeks, the increases in the bone mineral conte nt (BMC), BMD of the femur and tibia, and the bending load values of the fe mur were significant, but the climbing exercise did not increase BMC, BMD, or the compression load of the lumbar vertebra. Although the periosteal MS/ BS, MAR, and BFR/BS increased, the endosteal MS/BS, MAR, and BFR/BS decreas ed. These results show that climbing exercise has a beneficial effect on th e femoral cortex and tibia trabecular, rather than the vertebral trabecular . In the midfemur, effects on bone formation are site specific, supporting accelerated cortical drift by mechanical stimulation.