Wu Jian, Wang Xin Xiang, Higuchi Mitsuru, Yamada Kazuhiko, Ishimi Yoshiko
Division of Applied Food Research, The National Institute of Health and Nutrition, Tokyo 162-8636, Japan.
J Appl Physiol (1985). 2004 Sep;97(3):806-10. doi: 10.1152/japplphysiol.01169.2003. Epub 2004 Apr 16.
Exercise-induced bone gains are lost if exercise ceases. Therefore, continued exercise at a reduced frequency or intensity may be required to maintain these benefits. In this study, we evaluated whether 4 wk of reduced exercise after 4 wk of running exercise in growing male mice results in the maintenance of high bone mass. Five-week-old mice were divided into the following groups: 1) baseline control; 2) 4-wk control; 3) 4-wk exercise; 4) 8-wk control; 5) 4-wk exercise followed by 4-wk cessation of training; and 6) 4-wk exercise followed by reduced exercise at half the frequency. The regimen consisted of exercise 6 days/wk, and the reduced exercise regimen consisted of running 3 days/wk on a treadmill for 30 min/day, at 12 m/min on a 10 degrees uphill slope. Running exercise significantly increased bone mineral density of the femur, periosteal mineral apposition rate, bone formation rate, percent labeled perimeter at the midfemur, and osteogenic activity of bone marrow cells. However, these parameters declined to the age-matched sedentary control after cessation of training. In contrast, the reduced exercise group had significantly higher mineral apposition rate compared with those of the sedentary control and cessation of training groups. Furthermore, bone mineral density for the reduced exercise group was significantly higher than those for the other groups. These results suggest that the high bone formation gained through exercise can be maintained, and bone mass was further increased by subsequent exercise even if the exercise frequency is reduced.
如果停止运动，运动诱导的骨质增加就会消失。因此，可能需要以较低的频率或强度持续运动以维持这些益处。在本研究中，我们评估了生长中的雄性小鼠进行4周跑步运动后再进行4周减少运动量的运动是否能维持高骨量。将5周龄的小鼠分为以下几组：1）基线对照组；2）4周对照组；3）4周运动组；4）8周对照组；5）4周运动组后接着4周停止训练；6）4周运动组后接着以一半的频率进行减少运动量的运动。运动方案为每周6天运动，减少运动量的运动方案为每周在跑步机上跑3天，每天30分钟，速度为12米/分钟，坡度为10度上坡。跑步运动显著增加了股骨的骨矿物质密度、骨膜矿物质沉积率、骨形成率、股骨中段标记周长百分比以及骨髓细胞的成骨活性。然而，停止训练后，这些参数下降到与年龄匹配的久坐对照组水平。相比之下，减少运动量的运动组的矿物质沉积率显著高于久坐对照组和停止训练组。此外，减少运动量的运动组的骨矿物质密度显著高于其他组。这些结果表明，通过运动获得的高骨形成可以维持，并且即使运动频率降低，后续运动也能进一步增加骨量。
