Rest is not useless, and rational use is conducive to recovery. Excessive use will lead to the degradation of various functions. After soft tissue injury, there will be an acute phase within a week. Inflammation is active in the acute phase. We need to brake and rest to provide a good environment for soft tissue repair. However, after the acute stage, soft tissue repair entered the second stage, that is, the regeneration stage 2 ~ 6 weeks after injury. At this stage, more and more collagen fibers begin to grow in the damaged tissue to connect the damaged tissue. Later, I slowly entered the third stage, that is, the plastic surgery stage, which is about 6-8 weeks after the injury. Through reasonable functional mechanical stimulation, new tissue can be promoted to be closer to normal tissue.

Effect of immobilization on ligaments. Braking will lead to the decrease of collagen fiber output, the disorder of collagen fiber arrangement, the deterioration of physical structure and mechanical properties of new tissue, and the absorption of bone tissue at ligament attachment. Early controlled low-intensity exercise of injured ligament can improve the hardness and strength of scar and reduce scar hyperplasia and hypertrophy. Exercise can also increase the biomechanical function of the healing tissue, and make the new tissue closer to the normal tissue in various functions and structures.

Effect of fixation on cartilage. When I was a child, the nutrition of articular cartilage was provided in two parts, one from subchondral bone and the other from synovial fluid. In adulthood, the epiphyseal cartilage ossifies, leaving only synovial fluid for cartilage nutrition. However, this synovial fluid needs joint activities to provide nutrition, squeeze and relax cartilage, promote nutrient absorption of cartilage and discharge metabolic waste. This mechanism is called decentralization mechanism. Long-term fixation will lead to cartilage degeneration, dehydration and thinning. The recovery of articular cartilage can not be separated from mechanical stimulation. We need this exercise to provide the diffusion mechanism necessary for cartilage metabolism.

In addition, the slight wear of cartilage has certain repair ability, and this repair also depends on certain stress and friction stimulation. Effect of braking on bones. Bones include cancellous bone and cortical bone. There is trabecula in cancellous bone. Trabecular support and growth in the direction of maximum stress. After fracture, we need to stop at a certain stage, but after callus formation, we must gradually start loading. Long-term withdrawal of drugs will lead to bone loss, osteoporosis and hypercalcemia. Moreover, long-term immobility and bone stress stimulation are not conducive to fracture healing. Exercise contributes to the blood and metabolism of the whole body and promotes fracture healing.