EXERCISE CAN STRENGTHEN THE PREVENTING EFFECTS OF ESTROGEN ON OSTEOPOROSIS IN OVERIECTOMIZED RATS

1294 The effects of treadmill exercise and estrogen replacement therapy (ERT) on bony structures were studied using three different measurements: Cantiliver bending test (CBT), bone density (BD) and X-ray optical density (XOD). Sixty twelve-month old female Spraque-Dawley rats were assigned into six groups: ovariectomized control (OC); normal control (N); ovariectomized and ERT (0.1 mg/day) (OER); ovariectomized and reduced ERT (0.01 mg/day) (OE); ovariectomized and training (OT); ovariectomized, training and reduced ERT(0.01 mg/day) (OTE). The two exercise groups, OT and OTE, were trained 1h/day 3day/week for 12 weeks at 49 cm/sec and 12% gradient. Results revealed that OT has significantly higher maximal loading tolerance (MT) during CBT of femur neck than OC (36.270±6.226 g/g vs. 30.066±3.283 g/g). ERT groups have higher BD (OE:4.155±0.162, OER:4.297±0.44 g/cm3/Kg) than OC (4.086±0.347 g/cm3/Kg) but not statistically significant. There were no significant differences between OTE and N on both MT and BD measurements, but data of these two groups were significant higher than OT, OE, OER, and OC. Conclusions: Exercise mainly affects the biomechanical properties of bone, while ERT affects BD. The effects of ERT and exercise training might be interactive and additive in preventing osteoporosis.