Abstract
The effects of exercise training on bone development in growing rats were studied using the photon-absorption method and histomorophological analyses. Thirty-seven male Wistar strain rats at 4 wks of age were divided into five groups : sedentary control (C; N=7), 15 min/day training (T 15 ; N=6), 30 min/day training (T 30 ; N=8), 60 min/day training (T 60 ; N=8) and 120 min/day training (T 120 ; N=8) . All rats in these training groups were subjected to a treadmill running at a speed of 30 m/min, 5 days/wk for 11 wks. The results of our study were summarized as follows :
1) Fat-free dry weight of the tibia was significantly heavier in T 30, T 60 and T 120 than C and T 15, respectively.
2) Bone mineral content (mg/cm) of tibial midshaft in all T groups was significantly higher than that in C group, respectively, while no differences were found between any of the training groups.
3) On histological parameters of cross-sectional samples from tibia, such as cortical area, total area and appositional growth rate on periosteum, higher values were observed in T groups compared with C group.
These results suggest that physical training induce markedly facilitative girth growth associated with elevated bone formation of periosteum in the tibia, and moreover, the daily exercise duration does not change the degree of bone hypertrophy.
