Effect of long‐term voluntary running on bone tissue in mice

Background It is well known that exercise has positive effects on bone. It has been reported that voluntary exercise increase bone formation and bone density during growing period. However, effects of more long‐term exercise performed until adult on bone tissue are little known. Purpose To investigate the effects of long‐term voluntary wheel running on histological and mechanical properties of bone tissue in mice. Methods Four‐week‐old male C57BL/6 mice (n=31) were assigned to 1) a sedentary control (CON) and 2) a voluntary running (VE) groups. Mice in VE group were allowed free access a wheel. Femurs were removed at 4, 28, or 40 weeks of age. Bone volume was measured histologically as the bone volume per tissue volume［BV/TV (%)］, and bone strength was measured using three‐point bending test. Bone strength was normalized to body weight［N/g; maximum breaking force (N) per body weight (g)］. Results The body weight in the CON at 4, 28, 40 weeks of age was 18.4±0.5, 30.1±1.3, 29.8±1.4 g, respectively, while it in VE at 28 and 40 weeks of age was 26.7±0.8, and 29.2±2.4 g. BV/TV (%) significantly decreased with aging from 4 to 28 weeks of age in both groups. There were no significant differences in BV/TV (%) between CON and VE. Also, bone strength significantly increase with aging from 4 to 28 weeks of age in both groups. There were no significant differences between CON and VE. Conclusion Our data suggests that long‐term voluntary running do not effect on histological and mechanical properties of bone tissue in mice. This work was supported by grants from the MEXT‐Supported Program for the Strategic Research Foundation at Private Universities (S1101008).