What is the best exercise to do on a hot summer day? Running is full of sweat, health room and too boring, so many people may choose to swim. According to Pan Cuihuan, chief physician of the Department of Rehabilitation at the Second Hospital of Guangzhou Medical University, swimming is used as an ancient treatment method, and hydrotherapy is used to treat diseases and injuries in different people. Because the density of water is close to that of the human body, it can be used as a training medium for patients with paralysis, inflammation or muscle atrophy. The body is submerged in water and the hydrostatic pressure acts on the surface of the body to promote the return of peripheral venous and lymphatic fluid and the excretion of urine. Swimming on the human body also has the following major role 1, burn fat to maintain body shape Water sports require more coordination of the body, need to collaborate more muscles and joints in order to make the body coordinated, more muscles involved, plus the role of water resistance is also another important factor in the conversion of energy into kinetic energy; this is why the water environment can consume more energy, and each joint can get a balanced exercise, in This is why the water environment allows more energy to be expended and all joints to be exercised in a balanced manner, ensuring a ratio of dimension and strength in all parts of the body while reducing body fat percentage. In addition, the density of water is much greater than the density of air, the movement in the water need to overcome the resistance of the water to allow the body to move forward, helping the body’s energy is more into kinetic energy; water temperature is generally lower than the body temperature, even in the water at rest can also be conducted through the water temperature. For example, in the 12 ° of the water for 15 minutes in the heat loss is approximately equal to the heat loss of 1 hour on land. 2, the respiratory system to improve the ability of the water breath exchange can be seen as a form of deep breathing, it can effectively stimulate respiratory function, improve oxygen uptake capacity, etc.; water density is greater, in the water for exercise, the thoracic and abdominal cavity to withstand greater pressure, breathing more difficult, which is more demanding on the relevant respiratory muscle groups. Contraction and diastole to meet the oxygen demand when exercising in the water, so the respiratory function is improved. Therefore, long-term adherence to swimming people, oxygen uptake capacity, lung capacity, etc. can be effectively improved. 3, cardiovascular function is generally used during swimming horizontal position, venous blood flow to the heart more easily, so the venous return flow increased. In addition, in the above mentioned in the water environment breathing will deepen, which also means will increase the pumping effect on the venous return; in the water action is mostly a single repetitive action, muscle activity is more rhythmic, there is a squeezing effect on the veins. Secondly, the water has a massage effect on the skin and small blood vessels. Therefore, the water environment is conducive to venous reflux, can effectively improve cardiovascular function. 4, the joints are not easily damaged because there is no rapid start or braking action in the water environment, so the joint structure, ligaments, muscles, etc. are not easily damaged, and some deep muscles can also have a certain strengthening effect. Swimming can also be a very good rehabilitation exercise. The buoyancy of the water can help reduce the load of the swimmer’s joints for their own weight, helping to fully extend the flexion and reduce the weight of the joints for the squeezing effect. 5, thermoregulation ability to enhance the swimming water temperature is mostly lower than body temperature, so in the water environment can produce cold stimulation, through thermoregulation so that the body position of normal body temperature. Long-term activities in the water can make the heat production and heat dissipation process is improved, the body temperature regulation ability is enhanced. 6, adjust the mind to relieve stress Swimming activity is an effective way to regulate emotions. People in a stressful after work or in anxiety, depression, restlessness and other bad mood, just swim a few laps, through the friction and impact of the water on the body, can form a special massage, this natural massage, not only can make the muscles relaxed, but also make people soothe intoxicated in the embrace of nature. In this way, the tension of the nerves suddenly relaxed, get a better rest; at the same time, those negative, side effects on the body of the psychological factors excreted out, to restore a positive, healthy mental state.