Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, People's Republic of China.
National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology), Tianjin, People's Republic of China.
Comput Methods Biomech Biomed Engin. 2022 Nov;25(15):1757-1766. doi: 10.1080/10255842.2022.2037130. Epub 2022 Feb 16.
Osteoporosis occurs in astronauts after long-term space flight owing to the lack of gravity. The mechanical microenvironment of osteocytes in load-bearing bone are changed during resistance exercise, which prevents massive bone loss in the human body. A cylindrical fluid-structure coupling finite element model for osteons with a two-stage pore structure (i.e., Haversian canal, lacunar-canalicular system) was established with the software COMSOL. In the Earth's gravity field and in microgravity, considering the effects of pulsating pressure of arterioles, a comparative study was performed on the changes in hydrodynamic microenvironment of osteocytes during human body high-intensity exercise at different frequencies (defined as causing bone to produce 3000 με) and the body is at rest. Positive and negative liquid pressure (with respect to one atmosphere pressure) alternately acted on osteocytes during human exercising, but only positive pressure acted on osteocytes during human resting. The variation range of liquid pressure acted on osteocytes during human exercising was significantly higher than that during resting. The liquid flow velocity around osteocytes during body exercise was about four orders of magnitude higher than that during resting. In microgravity, moderate physical exercise can obviously improve the hydrodynamic microenvironment of osteocytes in load-bearing bone, which could compensate for the lack of mechanical stimulation to osteocytes caused by the lack of gravity, thereby promoting the normal physiological function of osteocytes. To a certain extent, these results revealed the biomechanical mechanism by which exercise has an effect in fighting osteoporosis in astronauts.
骨质疏松症在长期太空飞行的宇航员中发生，是由于缺乏重力。在抗阻运动过程中，承载骨中破骨细胞的机械微环境发生变化，防止了人体大量的骨丢失。采用软件 COMSOL 建立了具有两级孔隙结构（即哈弗氏管、骨陷窝-骨小管系统）的骨单位的圆柱体液-固耦合有限元模型。在地球重力场和微重力条件下，考虑到小动脉脉动压力的影响，对比研究了人体高强度运动（定义为引起骨产生 3000 με）不同频率和人体休息时破骨细胞的水动力微环境的变化。在人体运动过程中，正、负压（相对于一个大气压）交替作用于破骨细胞，但在人体休息时只有正压作用于破骨细胞。人体运动时作用于破骨细胞的液体压力变化范围明显高于休息时。人体运动时破骨细胞周围的液体流速比休息时高约四个数量级。在微重力条件下，适度的体育锻炼可明显改善承载骨中破骨细胞的水动力微环境，从而弥补因缺乏重力对破骨细胞机械刺激的不足，促进破骨细胞的正常生理功能。在一定程度上揭示了运动对抗宇航员骨质疏松症的生物力学机制。
