RESUMEN
The effects of the erect bipedal stance exercise on bone mass and the biomarkers of bone formation and resorption were investigated in rats. Five-week old rats were assigned into control and exercise groups. The rats of exercise group were weight-bearing-trained for 13 weeks in the cage designed to adjust progressively the height from 26.5 cm to 31.5 cm to force the rats rising an erect bipedal stance for feeding and drinking. There was no significant difference in food intakes between two groups. But body weight gain was significantly increased in control group. The lengths of femur, tibia, humerus and radius were significantly longer in control group than exercise group, but the femur and tibia weights per body weight were significantly higher in exercise group than control group. Also the breaking force of femur and tibia in exercise group were higher than control group significantly. The calcium contents of femur and tibia were significantly increased in exercise group than control group. The activity of bone specific alkaline phosphatase (B-ALP) and the osteocalcin contents of serum (the biomarkers of bone formation) in exercise group were higher than control group, but the carboxyterminal propeptide of type I procollagen (P1CP) contents of serum did not show any difference between two groups. However the urinary deoxypridinolin (DPD) excretion, biomarker of bone resorption, was significantly lower in exercise group than control group. From these results, it has been indicated that the erect bipedal stance exercise enhanced the density and the strength of femur and tibia by increasing biomarkers of bone formation and suppressing a biomarker of bone resorption in rats.