Influence on cardiovascular system: Swimming plays an important role in improving cardiovascular system. The stimulation of cold water can promote blood circulation through heat regulation and metabolism; In addition, the pressure and resistance of water also play a special role in the heart and blood circulation. When swimming on the water, the water pressure on the body has reached 0.02-0.05 kg per square centimeter. When diving, with the increase of depth and the change of physical conditions, the pressure will increase, and the speed of swimming will also increase the pressure load. The muscle tissue of atrium and ventricle can be strengthened, the volume of heart cavity can be gradually increased, and the beating times of heart can be reduced. This can preserve the activity of the heart, but it can improve the whole blood circulation system. When resting, systolic blood pressure increases, systolic blood pressure decreases, and blood pressure value becomes more favorable. The elasticity of blood vessels has also improved. According to the statistics of relevant experts, the average person's heart beats about 66-72 times per minute in a quiet state, and the stroke output is about 60-80 ml, while those who take part in swimming exercises for a long time contract about 50 times under the same conditions, but the stroke output reaches 90- 120 ml. Influence on respiratory system: During swimming practice, without a large amount of oxygen supply, the metabolic process and cardiovascular system can't be saved. However, because water compresses the chest and abdomen, it is more difficult to inhale. Someone has done special experiments. When swimming, people's chest is under the pressure of 12- 15 kg of water, so in order to get enough oxygen for the body, the respiratory muscles must constantly overcome this pressure. In addition, when swimming, exhalation is generally done underwater, and the density of water is much higher than that of air, so it is necessary to use force to exhale, so that both inhalation and exhalation can increase the contraction force of respiratory muscles, thus enhancing the function of respiratory system and increasing vital capacity. The average healthy person's vital capacity is 3000-4000 ml, while those who often swim can reach 5000-6000 ml. Influence on human skin: In the swimming process, due to the stimulation of water temperature, the human body wants to ensure sufficient temperature. Skin blood vessels play an important regulatory role. Stimulation of cold water can make skin blood vessels contract and prevent heat from spreading outward. At the same time, the body will intensify the generation of heat, dilate the blood vessels of the skin and improve the blood supply of the blood vessels of the skin, so that long-term exercise can strengthen the blood circulation of the skin. In addition, water is a very soft liquid. Because of the action of water waves, it constantly rubs the human epidermis and makes the skin relax and rest better, so people who often take part in swimming exercises have smooth and soft skin. Other functions: As we all know, we live in a sphere filled with three quarters of water, so it is inevitable to deal with water in our life. This is that swimming is not only a sport, but also a rare tool and skill in life. It permeates many fields of our lives, such as water resources development, scientific investigation, flood control and salvage. All this must be backed by skilled swimming skills to ensure life.