Bennell Kim L, Khan Karim M, Warmington Stuart, Forwood Mark R, Coleman Brett D, Bennett Michael B, Wark John D
Centre for Sports Medicine Research and Education, School of Physiotherapy, University of Melbourne, 200 Berkeley St., Carlton, 3052, Victoria, Australia.
Med Sci Sports Exerc. 2002 Dec;34(12):1958-65. doi: 10.1097/00005768-200212000-00015.
Because it is believed that bone may respond to exercise differently at different ages, we compared bone responses in immature and mature rats after 12 wk of treadmill running.
Twenty-two immature (5-wk-old) and 21 mature (17-wk-old) female Sprague Dawley rats were randomized into a running (trained, P = 10 immature, 9 mature) or a control group (controls, P = 12 immature, 12 mature) before sacrifice 12 wk later. Rats ran on a treadmill five times per week for 60-70 min at speeds up to 26 m.min. Both at baseline and after intervention, we measured total body, lumbar spine, and proximal femoral bone mineral, as well as total body soft tissue composition using dual-energy x-ray absorptiometry (DXA). After sacrificing the animals, we measured dynamic and static histomorphometry and three-point bending strength of the tibia.
Running training was associated with greater differences in tibial subperiosteal area, cortical cross-sectional area, peak load, stiffness, and moment of inertia in immature and mature rats (P < 0.05). The trained rats had greater periosteal bone formation rates (P < 0.01) than controls, but there was no difference in tibial trabecular bone histomorphometry. Similar running-related gains were seen in DXA lumbar spine area (P = 0.04) and bone mineral content (BMC; P = 0.03) at both ages. For total body bone area and BMC, the immature trained group increased significantly compared with controls (P < 0.05), whereas the mature trained group gained less than did controls (P < 0.01).
In this model, where a similar physical training program was performed by immature and mature female rats, we demonstrated that both age groups were sensitive to loading and that bone strength gains appeared to result more from changes in bone geometry than from improved material properties.
由于人们认为骨骼在不同年龄对运动的反应可能不同，我们比较了未成熟和成熟大鼠在跑步机上跑步12周后的骨骼反应。
将22只未成熟（5周龄）和21只成熟（17周龄）雌性Sprague Dawley大鼠随机分为跑步组（训练组，未成熟10只，成熟9只）或对照组（对照组，未成熟12只，成熟12只），12周后处死。大鼠每周在跑步机上跑5次，每次60 - 70分钟，速度可达26米/分钟。在基线和干预后，我们使用双能X线吸收法（DXA）测量全身、腰椎和近端股骨的骨矿物质，以及全身软组织成分。处死动物后，我们测量了胫骨的动态和静态组织形态计量学以及三点弯曲强度。
跑步训练与未成熟和成熟大鼠胫骨骨膜下面积、皮质横截面积、峰值负荷、刚度和惯性矩的更大差异相关（P < 0.05）。训练组大鼠的骨膜骨形成率高于对照组（P < 0.01），但胫骨小梁骨组织形态计量学无差异。在两个年龄段，DXA测量的腰椎面积（P = 0.04）和骨矿物质含量（BMC；P = 0.03）都有类似的与跑步相关的增加。对于全身骨面积和BMC，未成熟训练组与对照组相比显著增加（P < 0.05），而成熟训练组的增加少于对照组（P < 0.01）。
在这个模型中，未成熟和成熟雌性大鼠进行了相似的体育训练计划，我们证明两个年龄组对负荷都敏感，并且骨强度的增加似乎更多是由于骨几何形状的变化而不是材料特性的改善。
