Leg cramps usually occur when muscles are tired, which is suddenly caused by cold air and cold water. Because the human body will also be cold because of sweating, and convulsions will occur in summer; In addition, when exercising, tired feet encounter cold air, sweating makes the body cold and muscles suddenly stretch. At this time, the output is easy to cause cramps. Generally speaking, the most common cause of cramps is insufficient warm-up. The most typical sport is swimming. How to prevent cramps when swimming again, the most important thing is to warm up and let the body gradually adapt to the change of water temperature. This is because when the difference between body temperature and outside temperature is more than 7 degrees, and it is sudden contact, it often causes cramps.