Effects of Loading Frequency on the Mechanical Response Properties of Osteocytes in Microgravity Environment

This study explored the underlying causes of weightless bone loss in astronauts long-term space flight. Under the earth gravitational field (1 g) and the microgravity field (0 g), cyclic loading of different frequencies (0.1 Hz, 0.2 Hz, 0.5 Hz) was acted to finite element model of osteon respectively, and a comparative study of fluid pressure, velocity and stress in osteocyte was made. The effect of loading with frequency 0-0.6 Hz on the stress extremum of osteocytes in microgravity environment was studied by curve fitting. The results showed that the significant liquid pressure gradient in the osteocytes within the earth gravity field, compared with the 0 g gravity field, and the fluid pressure, the stress and flow rate of the osteocyte increased with the increase of the loading frequencies. Both the increase of the gravitational field and the loading frequencies can increase the mechanical induction of osteocytes, which was more likely to cause bone remodeling and achieve bone balance. This study is expected to explain mechanical response on osteocytes within microgravity can be a cause of osteoporosis in astronauts from the perspective of biomechanics. Astronauts in space can reduce osteoporosis by physical exercises to some extent and provide theoretical guidance for subsequent research on confrontation.