The changes in skeletal muscle calcium ions during bed rest or early braking are mainly the increased uptake and release of calcium ions by the sarcoplasmic reticulum, which will directly affect the contractile function of skeletal muscle. Histological observation showed that 7 days of braking, the connective tissue between muscle fibers proliferated, and the muscle fibers became thin and disordered in arrangement. Electron microscopy revealed significant mitochondrial swelling with crystal formation. In brief, the change that occurs in the muscle early in braking is atrophy, i.e., a decrease in the weight of the entire muscle. The atrophied muscles show a decrease in muscle strength. With prolonged bed rest or braking, the volume of the muscle decreases (tape measure limb circumference becomes smaller), the tension per unit area of the muscle decreases (muscle pulling sensation is obvious during joint movement), while the excitability of motor nerves decreases, the recruitment of motor units decreases (completion of movement is delayed), the muscle cannot contract normally and is easily fatigued. This is the general cause of muscle weakness. Changes in the internal functional state of muscles after braking also directly affect muscle strength: as muscle glycogen and ATP stores decrease, doing work makes muscle glycogen and ATP rapidly depleted, lactic acid content increases, and fatty acid antioxidant capacity decreases, resulting in rapid muscle fatigue; decreased blood flow to muscles and lack of oxygen are also factors.