1. exercise system: physical exercise accelerates the blood circulation of human body, improves the blood supply in bone tissue during osteogenesis, enables it to obtain more nutrition and accelerate the process of osteogenesis. It is not a problem for children to grow taller! 2. Cardiovascular system: Children and adolescents actively participate in physical exercise, which can promote the development of cardiovascular system and improve its functional level. The workload of the heart increases during exercise, which makes the heart rate increase appropriately and the blood flow increase. Exercise of myocardium, improvement of coronary artery and adequate nutrition of myocardium will lead to the development of myocardium, thickening of ventricular wall and increase of heart volume in the long run. 3. Respiratory system: When the human body is exercising, the carbon dioxide produced by muscles can stimulate the respiratory center, accelerate and deepen breathing, thus promoting the elimination of carbon dioxide and the inhalation of oxygen. Children and adolescents often engage in sports, which can promote the development of their respiratory system and improve their functional level, mainly in the following aspects: developed respiratory muscles, increased chest circumference, increased breathing difference, increased breathing depth, increased lung ventilation and vital capacity. 4. Nervous system: Children who often participate in physical exercise can master a variety of motor skills, improve the coordination of muscle work, and improve their sports ability and technical level. It is the enhancement of nerve excitement and inhibition. Exercise can enhance resistance and improve functional adaptability, but only by paying attention to moderation and moderation can it play a role in fitness.