BACKGROUND Bone is a dynamically hierarchical material that can be divided into length scales of several orders of magnitude. Exercise can cause bone deformation, which in turn affects bone mass and structure. This study aimed to study the effects of treadmill running with different intensities on the long bone integrity and muscle biomechanical properties of adult male rats. METHODS Forty-eight 5-month-old male SD rats were randomly divided into 4 groups: i.e., sedentary group (SED), exercise with speed of 12 m/min group (EX12), 16 m/min group (EX16), and 20 m/min group (EX20). The exercise was carried out for 30 min every day, 5 days a week for 4 weeks. The femurs were examined using three-point bending test, microcomputer tomography scanning and nanoindentation test; the soleus muscle was dissected for tensile test; ALP and TRACP concentrations were measured by serum analysis. RESULTS The failure load was significantly increased by the EX12 group, whereas the elastic modulus was not significantly changed. The microstructure and mineral densities of the trabecular and cortical bone were significantly improved by the EX12 group. The mechanical properties of the soleus muscle were significantly increased by treadmill exercise. Bone formation showed significant increase by the EX12 group. Statistically higher nanomechanical properties of cortical bone were detected in the EX12 group. CONCLUSION The speed of 12 m/min resulted in significant changes in the microstructure and biomechanical properties of bone; besides, it significantly increased the ultimate load of the soleus muscle. The different intensities of treadmill running in this study provide an experimental basis for the selection of exercise intensity for adult male rats.

中文翻译：

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不同强度的跑步机对成年大鼠骨质量和肌肉特性的影响。

背景技术骨是一种动态分层的材料，可以分为几个数量级的长度尺度。运动会导致骨骼变形，进而影响骨骼质量和结构。这项研究旨在研究不同强度的跑步机对成年雄性大鼠长骨完整性和肌肉生物力学特性的影响。方法将48只5个月大的雄性SD大鼠随机分为4组：久坐组（SED），以12 m / min的速度运动组（EX12），以16 m / min的速度运动组（EX16）和20 m / min组（EX20）。该运动每天进行30分钟，每周5天，共4周。用三点弯曲试验，微型计算机断层扫描和纳米压痕试验检查股骨。解剖比目鱼肌进行拉伸试验；通过血清分析测量ALP和TRACP浓度。结果EX12组的破坏载荷显着增加，而弹性模量没有显着变化。EX12组显着改善了小梁和皮质骨的微观结构和矿物质密度。比目鱼肌的机械性能通过跑步机运动得到显着提高。EX12组的骨形成显示明显增加。在EX12组中检测到统计上更高的皮质骨纳米力学性能。结论12 m / min的速度导致骨骼的微观结构和生物力学特性发生了显着变化。此外，它显着增加了比目鱼肌的极限负荷。