Limitation of left chest pain caused by extending the arm back is a consideration for soft tissue injuries to the chest muscles, including the pectoralis major, pectoralis minor, intercostal muscles, and other muscle groups. Extension of the arm back will pull on the chest muscles such as pectoralis major, pectoralis minor or intercostal muscles, and extension of the arm back will overstretch the chest muscles, which will lead to muscle injury in the long run. The muscle abdomen or muscle attachment point of the injured muscle is in a localized ischemic and hypoxic state, forming aseptic inflammation, and the aseptic inflammatory reaction will cause obvious chest pain. Due to excessive stretching caused by the left chest muscle pain can be in the local hot compresses, avoid the upper limb back stretching force, if still not relieved, it is recommended that the patient to go to the hospital to find out the cause of the symptomatic treatment.