The effect of periodic stretching on countering bone loss in hindlimb unloading rat

Introduction: Conventional exercises could not prevent the deterioration of astronaut's bone and muscle effectively during space flight. On the ground, stretching is widely used to improve the joint range of motion (ROM) and muscle performance. However, study on how stretching affected bone mass and bone quality was rarely reported and the animal stretching modes were not ideal. Therefore, the aim of this study was to develop a device that stretching the hindlimb of rats to study the effects of stretching on bone in hindlimb unloading rats. Methods: The ankle joint angel of conscious rat was kept at 30 degrees for periodical stretching by this device. 32 Sprague Dawley rats were randomly divided into 4 groups (n = 8, each): control group (CON); CON plus stretching group (CONS); tail-suspension group (TS); TS plus stretching group (TSS). On the 29th day of the experiment, the bone mineral density (BMD) and trabecular microstructure were analyzed by mu CT, the mechanical properties of tibia were determined by three-point bending test and the muscle performance was measured by multi-channel physiological signal tester. Results: The data showed that the muscle strength and wet weight in TSS group were significantly higher than TS group. After stretching, the BMD, trabecular microstructure and mechanical properties of tibia in TSS group were also significantly better than TS group. In addition, these results of bone showed no significant difference between TSS group and CON group. Conclusions: This device we developed could quantitatively stretch the hindlimb of rat and prevent the bone and muscle degeneration induced by tail-suspension. Our results suggested that stretching could be a useful exercise mode to keep bone and muscle healthy for astronauts or people who could not do conventional exercise.

Automated summary

This study developed a device for stretching the hindlimb of rats to study the effects of stretching on bone in hindlimb unloading rats. The results showed that stretching improved bone density, muscle strength, and mechanical properties, and could prevent bone and muscle degeneration induced by tail-suspension. These findings suggest that stretching could be a useful exercise mode for maintaining bone and muscle health in astronauts or individuals unable to do conventional exercise.