Interrupted vs. Uninterrupted Training on BMD during Growth

Abstract This study compared a resistance training program where the exercise was uninterrupted (UT, i.e., continuous repetitions) against a resistance training program where the exercise was interrupted (IT, i.e., 3 exercise sessions during a training day) for enhancing bone modeling and bone mineral density (BMD) in maturating animals. The total volume of work performed between the two resistance training programs was equivalent by design. 24 young male rats were randomly divided into Control (Con, n = 8), UT (n = 8) and IT (n = 8) resistance trained groups. The UT and IT groups were conditioned to climb a vertical ladder with weights appended to their tail 3 days/wk for 6 wks. After the 6-wk program, serum osteocalcin was not significantly different between groups, whereas the adjusted urinary deoxypyridinoline (DPD) was significantly lower for both UT (81.03 ± 5.53) and IT (88.30 ± 7.29) compared to Con (128.13 ± 9.99). Tibial BMD (assessed via DXA) was significantly greater for UT (0.222 ± 0.005 g/cm 2 ) and IT (0.219 ± 0.003 g/cm 2 ) when compared to Con (0.205 ± 0.004 g/cm 2 ). There was no significant difference in DPD or BMD between UT and IT groups. The results indicate that both interrupted and continuous, uninterrupted resistance training programs were equally effective in stimulating bone modeling.