| Bone loss of weightlessness, that is persistent bone loss and negative calcium balance phenomenon in astronauts which is caused by weightless environment of space flight. Bone loss of weightlessness is one of the main obstacles in human space exploration. It's primarily manifests are bone loss, bone demineralization, reduced bone mineral density and decreased mechanical properties of bone biology and so on. Osteoporosis (OP) is a disease which is characterized by bone mass reduction, bone tissue micro-structural damage, bone fragility, high incidence of fracture and so on. However, exercise intervention in bone development as a positive means, has been valued by the academic community. Exercise can increase bone mass, maintain bone mass and reduce the loss of bone mass, therefore, participate actively in physical exercise can cause the bone development healthily. The study shows that reasonable exercises can promote bone development, and improve the function of bone mineral density, bone structure and biomechanical properties.This study aims to find out the mechanism of treadmill movement patterns on bone metabolism in rats and analyze the differences in bone metabolism of these two exercise modes by comparing with swimming. In this paper, we use quantitative research in minor structural changes in rat skeletal, and also analysis reasons for its cause, so as to provide a reasonable theoretical basis for thinking and working in astronaut rehabilitation training.[Objective]1. Set up an ideal rat tail-suspension model, find out the impact of internal control mechanism of tail-suspension model on bone mineral density and bone metabolism. Tail-suspension method is a good experimental model on the study of osteoporosis. Therefore, we set up the appropriate animal model to study the pathogenesis of osteoporosis. At the same time, we are looking for effective control methods for it.2. Study the effects of different forms of exercise after simulated weightlessness on bone mineral density, bone histomorphometry, bone biomechanics, etc. So as to provide a theoretical basis on exercise interventions selection and exercise prescriptions formulation3. Study the effects of running and swimming on bone mineral density in rats.4. Study the effects of running and swimming on bone histomorphometry in rats.5. Study the effects of running and swimming on bone biomechanics in rats.[Methods]1. set up animal model of tail-suspended installations. Medical adhesive tape will be tightly wrapped around the tail and connected with key ring, which can be rotated to prevent the tail from twisting; with the continuous growth of rats, it is necessary to mediate the height of tail-suspended.2. Observation on the rat model: Observe the activities, diet, bodyweight, color and luster of rat's hair during experiment.3. Basic physical items of tibiae and femur of leftMeasure tibiae and femur's thickness, width and length by Necrosis.4. Measurement of BMD:Measure BMD by HOLOGIC Discover A.5. Bone biomechanical (structural and material mechanics) indicators measuring Adjust the pressure head and execute three-point bending experiments by using INSTRONG-8874-J9785.[Results]1. The results of the basic situation of rats: with a healthy growth during the suspension, eat freely, non-violent, but the body weight is lighter than control group with a significant difference; The body weight of rats increased during campaign period, and running group is heavier than swimming group also with a significant difference.2. The body weight of simulated weightlessness rat is significantly lower than the quiet group with a very significant difference; femur and lumbar spine BMD should be lower than the control group with significant differences; tibia and lumbar spine biomechanics indicators also decreased significantly.3. Femur length of treadmill exercise group is longer than free restoration group, with significant difference. The remaining indicators is quiet with no significant difference compared with quiet group.4. The BMD of Femur and lumbar bone in treadmill training group and swimming training group has significant difference compared with the restoration group.5. The treadmill training group has better lumbar biomechanical properties and tibia biomechanical properties as compared with the control group. The swimming group has better indexes of lumbar bone biomechanical properties as compared with the control group, also there was little increase in the tibia biomechanical properties compared with the control group.[conclusion]1. This experiment successfully established the model of simulated weightlessness in rats. It studied the effects of different forms of exercise on the role of bone metabolism in rats, so as to provide a good theoretical basis of the weight loss resumed.2. Suspension model has a degradation function on bone mineral density, bone histomorphometry, and bone biomechanics.3. Four weeks of swimming training increased the bone mineral density and biomechanical properties of the femur and lumbar of mice greatly, but there is no obvious impact on the femur and tibia histomorphometry.4. Four weeks of treadmill training increased bone mineral density of femur and lumbar spine, bio-mechanics as well as the femur histomorphometry of the femur length indicators significantly.5. Different forms of movement have obvious different effects on bone metabolism: The effect of treadmill movement in general is superior to swimming training group. But the swimming training seem more reasonable and better in bone mineral density of the lumbar spine.6. Movement can be effective in rats after simulated weightlessness, promote bone growth, increased body bone mineral density, improve bone histomorphometry, bone biomechanics indicators, in order to further study the prevention and treatment of weight loss and other symptoms of osteoporosis and provide theoretical support.
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