Swimming is carried out in water, and the density and thermal conductivity of water are different from air. The density of water is 800 times that of air, and its thermal conductivity, pressure and resistance are all greater than that of air. Therefore, swimming has a positive effect on human metabolism, body temperature regulation, cardiovascular system, respiratory system, muscle system, growth and development, and delaying aging. (1) Swimming can improve cardiopulmonary function. When swimming, people lie in the water. Because of the buoyancy of water, people weigh only a few kilograms in water. When people exercise on land, all organs must bear much more weight than in water. In contrast, the load when swimming is much less than that brought by land activities. Lying flat in water can also reduce the resistance of blood circulation system and the load of supporting organs. When swimming, all postures require full extension of the spine, which is very effective in preventing hunchback and scoliosis. Swimming can also enhance the function of the respiratory system. When swimming, people's chest and abdomen are under the pressure of water. When swimming, the pressure on the chest is 120 ~ 150 Newton, which makes breathing difficult. Long-term swimming exercise can increase breathing depth and vital capacity. The vital capacity of excellent swimmers can reach 5000 ~ 7000 ml, while that of normal healthy men is about 3500 ml. Taking part in swimming exercise can improve the adaptability to water temperature and air temperature and enhance physical fitness. Many children with asthma have strengthened their physique and resistance to cold by swimming, reduced the number of asthma attacks and even cured asthma. Swimming can also effectively improve and improve the function of people's cardiovascular system, especially taking part in swimming exercise from an early age, which can promote the development of cardiovascular system, which is irreplaceable by other sports. When a person lies flat to stand still, due to the effect of gravity on blood, the blood accumulated in leg veins is about 600 ml, so the heart volume decreases. At this time, the body has to speed up the heart rate to maintain the heart's blood output per minute. This is why the heart rate is faster when standing than when lying down, and the heart volume is smaller (about 600 ml). On the contrary, when you change from standing to lying, the hydrostatic pressure in your body decreases and blood flows from all parts of your body to your chest. Because gravity reduces the pressure on the heart, blood flows back to the heart more easily than when standing, so the heart volume increases by about 740 ml and the heart rate slows down. When swimming, you will feel weightless because the hydrostatic pressure in your body is offset by the buoyancy of water. The pressure of water will push 700 ml of blood in the superficial vein back to the chest cavity, so the central venous pressure will increase significantly. Results The cardiac blood flow increased, the cardiac volume increased (to about 840 ml), and the heart rate slowed down accordingly. Long-term swimming, especially long-term swimming, can effectively increase the heart volume and reduce the heart rate at rest. An excellent athlete's pulse in the morning can reach about 40 times/minute. Function preservation occurs when quantitative work is completed. Swimming can also increase the elasticity of blood vessel wall, increase the number of capillaries, obviously improve the function of circulatory system, keep blood pressure in a good state, and obviously increase the pulse pressure difference. Swimming can effectively consume body fat, especially swimming for a long time, because the difference between water temperature and body temperature is about 10 degrees Celsius, which will accelerate the heat dissipation of human body and increase consumption. Many people feel hungry or hungry after swimming. Swimming combined with diet control is undoubtedly a good way to lose weight. Experiments show that swimming consumes more calories than long-distance running, gymnastics and wrestling athletes. The heat dissipation of swimming at 20℃ is five times that of basal metabolism, and the heat consumption of swimming at 5℃ for five minutes is equivalent to that of long-distance running on land 1 hour. Modern scientific research shows that there is a cell called T lymphocyte in human immune function, and its activity and quantity are decreasing with age. Therefore, people are prone to some diseases after middle age, such as stomach disease, duodenal ulcer, coronary heart disease, hypercholesterolemia, rheumatoid arthritis, hyperosteogeny, bronchitis, tumor and so on. The occurrence of these diseases is closely related to the decline of human immune function, and insisting on swimming or cold water swimming (winter swimming) is one of the most effective prescriptions. Swimming also has the effect of beauty and skin care. Swimming is carried out in water, and long-term high humidity environment is beneficial to skin moisturizing and maintenance. When the water content of skin is lower than 10%, the skin is dry and rough. Swimming can not only moisturize, but also massage the skin! People who often do swimming training have plump chest muscles, wide shoulders, wide shoulders and narrow hips, and elastic muscles give people a strong and symmetrical natural beauty. (2) Swimming is a good way to educate children. In the 1990s, when the only child was born, many parents felt headache because of their fatal weakness, such as their inability to endure hardship and weak will. 1997 During the summer vacation, parents who sent their children to swimming classes were investigated. Most parents let their children learn swimming not only to learn a self-protection skill, but also to exercise. More importantly, they let children exercise their willpower in the process of learning to swim and cultivate good habits of obeying discipline. Learning to swim is a collective activity and a competition, and the learning speed is limited by time. Children who learn quickly and well are admirable, while children who learn slowly naturally have a kind of pressure. Many children who learn to swim are 6-7 years old. It is good for them to get used to moderate stress when they are young. The first step in learning to swim is to overcome the fear of water, and with the progress of teaching activities, we must also overcome the fear of suffering, cold and fatigue. With the overcoming of bad psychology, children's self-control ability will be improved, good qualities such as self-confidence, perseverance and courage will be cultivated, and good habits such as discipline, order and mutual assistance will also be formed, which will play a positive role in the cultivation of children's ideological quality. (3) Swimming is a good way for the elderly to keep fit. Swimming load intensity is relatively low, which is a good way for the elderly to entertain and keep fit. Old people who take part in water sports are not necessarily good swimmers. Walking in the water or carrying a lifebuoy can achieve the purpose of exercising. Old people who are too fat to move on land can exercise by buoyancy in water, thus enhancing muscle strength, promoting cardiovascular function and improving the flexibility and flexibility of joint ligaments. At the same time, water sports are beneficial to the treatment of chronic diseases and physical recovery of the elderly. The participation of the elderly in swimming activities has been highly valued by all countries in the world. 1986 The 1 World Swimming Competition, including water polo and diving, was held in Tokyo, Japan. Two years later, the third meeting was held in Brisbane, Australia. Twenty-five countries sent teams of more than 4,000 athletes. Among them, the oldest is 90-year-old Australian swimmer Vera Fernandez, who participated in the 50-meter freestyle competition. An 89-year-old man from Japan also took part in the competition. The final is a mixed relay race, consisting of two men and two women. The intensity and lively scenes of the game are no worse than those of young people. Water fitness for the elderly is very common in some countries in Europe and America. People call it "hydrotherapy" The fitness department specially offers water sports classes for the elderly, teaching various water sports methods and their effects on various parts of the body. According to the statistics of Louisiana, the number of elderly people participating in water sports is increasing exponentially because of its good effect. Considering the increasing population of the elderly, some countries pay more and more attention to the health of the elderly, and list the water sports of the elderly as a development project in 2 1 century. (4) Swimming is a pressure on young people and a panacea for restoring energy. Swimming is a good means to regulate mood. People are often in a state of anxiety, melancholy and impetuousness in stressful work. As long as you swim in the water a few times, a special massage method is formed through the friction and impact of the water flow on the body. This natural massage can not only relax muscles, but also immediately relax the nervous system, expel negative psychological factors that have side effects on the body and restore a positive and healthy psychological state. Swimming is a very social sport, and most participants walk together. Swimming in one place for a long time will make new friends, and these people will get together to chat and take care of each other, which will make people mentally satisfied.