Resistance Training Threshold for Elevating Bone Mineral Density in Growing Female Rats

The purpose of this study was to determine the minimum amount of resistance exercise that would stimulate bone formation yielding an elevation in bone mineral density (BMD) during the growth period in female rats. Female rats were randomly divided into: Control (Con, n = 8), 3 ladder climb resistance-trained group (3LC, n = 8), 4 ladder climb resistance-trained group (4LC, n = 8), 5 ladder climb resistance-trained group (5LC, n = 8), and 6 ladder climb resistance-trained group (6LC, n = 8). All exercised groups were conditioned to climb a vertical ladder with weights appended to their tail 3 days/wk for a total of 6 wks. After 6 wks, left tibia BMD (g/cm(2)) was significantly greater for 4LC (0.197 +/- 0.003), 5LC (0.200 +/- 0.004) and 6LC (0.202 +/- 0.003) when compared to Con (0.185 +/- 0.006). Left femur BMD (g/cm(2)) was significantly greater for 4LC (0.260 +/- 0.005), 5LC (0.269 +/- 0.004) and 6LC (0.272 +/- 0.006) when compared to Con (0.244 +/- 0.006). There were no significant differences in tibia and femur BMD between 4LC, 5LC, and 6LC groups. The results suggest that during growth, a high volume of resistance exercise was required to elicit an elevation in BMD in females.