People who don't usually do much exercise, after taking part in strenuous exercise such as mountain climbing and long-distance running, consume energy in leg muscles and accumulate a lot of lactic acid in muscle tissue, which leads to soreness in the next few days. The immediate solution is to apply a hot towel to the leg muscles and massage gently to help accelerate the absorption and decomposition of lactic acid, which can alleviate it. The long-term solution is to insist on taking part in exercise to adapt the body, so that lactic acid is produced less and the pain is less, and even if it hurts, it will recover quickly.