The best time for swimming is 20 to 45 minutes at a time. Don't be greedy for a long time, which will affect your health. In addition, if you swim in the swimming pool, your body will get sick due to chlorine invasion due to long-term immersion in water. Most tap water used in modern cities is disinfected with chlorine.
Therefore, people are directly exposed to chlorine when swimming, and these substances will evaporate from the water and be directly absorbed by the skin. ? Generally, the absorption of chlorine within 20 minutes has little effect on human body, but with the increase of time, it may lead to human illness.
Precautions for swimming
The human body dissipates heat easily in water. In order to avoid excessive heat dissipation, the human body will produce protective reflex, which will lead to contraction of skin blood vessels. So the skin will turn white when you first enter the water. After swimming in the water for a period of time, your blood circulation will be accelerated, your calories will increase, and your skin will turn from white to red.
If you stay in the water for too long, the heat generated by your body will be lower than the heat emitted in the water, and your thermoregulation function will be destroyed. Arteries in your skin will contract, venules will expand, causing blood to stagnate in subcutaneous veins, leading to blue skin, black lips, goose bumps and even spasms.
Once this happens, swimmers must go ashore immediately, dry their bodies, bask in the sun, and get dressed as soon as possible after keeping warm to prevent colds, muscle strain and other diseases.