[Show abstract][Hide abstract] ABSTRACT: Running exercise is an effective therapy for the prevention of osteoporosis; however, appropriate duration of exercise has not been determined. We therefore investigated the effect of exercise duration on bone mineral density (BMD) and systemic bone metabolism using young growing rats. Fifteen 8-week-old female Wistar rats were divided into three groups according to running load: control group (no running), short duration (30 min/day) and long duration (180 min/day), and animals ran on a treadmill 5 days per week over an 8-week period. BMD of the tibia was measured using peripheral quantitative computed tomography, and serum levels of tartarate-resistant acid phosphatase (TRAP), a bone resorption marker and alkaline phosphatase (ALP), a bone formation marker were measured to know whether the treadmill exercise would affect systemic bone metabolism. Short-duration running exercise (30 min/day) caused a significant increase in BMD of the metaphyseal trabecula (p < 0.05) with a reduction of serum TRAP levels (p < 0.01) and an increase in serum levels of calcium (p < 0.05) and phosphorus (p < 0.01). Conversely, long-duration exercise (180 min/day) significantly reduced BMD of the diaphyseal and metaphyseal cortex and that of the diaphyseal trabecula with a significant reduction of serum ALP levels and a significant increase in serum phosphorus. These findings suggest that short-duration exercise may increase BMD through suppression of bone resorption, whereas long-duration exercise may reduce BMD through suppression of bone formation. Exercising for short duration but not prolonged exercise is recommended to increase BMD of loaded long bones.
No preview · Article · Oct 2009 · The Tohoku Journal of Experimental Medicine
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to examine the effect of different frequencies of running exercise on increasing bone mineral density (BMD) and improving bone histomorphology at various sites of the skeleton (tibia, femur, and second lumbar vertebra) in young rats. Twenty-five female Wistar rats, 8 weeks old, were divided into five groups, of 5 animals each according to running load: control group, no running (A group); running load (RL), 4 days per week (d/w; B group); RL, 5 d/w (C group); RL, 6 d/w (D group); and RL, 7 d/w (E group). Rats ran on a treadmill at a speed of 15 m/min for 30 min per day over an 8-week period. The results indicated that the BMD of the tibia in the B, C, D, and E groups and that of the femur in the B and E groups increased significantly over that of the A group. However, the cortical BMD and trabecular BMD of the second lumbar vertebra did not change. In regard to bone histomorphometry of the tibia, a parameter of bone resorption (eroded surface/bone surface) was significantly lower in the B and D groups than in the A group. There were no differences in the parameters of bone formation. Tartaric acid-resistant acid phosphatase (TRACP) values were significantly lower in the B and C groups than in the A group. There were significant increases in body weight in the B group and in muscle weight in the C group. From the data obtained in this study, it was concluded that increases in BMD were obtained by a moderate running load at frequencies of 4 and 5 days per week.
Preview · Article · Feb 2005 · Journal of Bone and Mineral Metabolism