Muscle strain refers to the injury caused by the tearing of muscle fibers. It is mainly caused by excessive exercise or insufficient warm-up. The severity of the injury can be known according to the degree of pain. Once the pain is induced, stop exercising immediately, and apply ice cubes or cold towels to the pain points for 30 minutes to make the small blood vessels contract and relieve local congestion and edema. Avoid rubbing and hot compress.