Left back pain is usually caused by several reasons: first, muscle strain, over-activity of the left upper limb as well as the left shoulder joint will cause severe strain on the trapezius and rhomboid muscles around the scapula, and the patient will show significant pain and stiffness in the back of the left scapula, the left shoulder joint and scapula will be significantly restricted in movement, and the pain symptoms are especially severe when pressed. Sometimes a large number of scattered spastic hard nodes can be found in the muscle, which are painful when pressed. Second, cervical spondylosis, cervical spondylosis attack can compress the nerve roots, stimulate the nerve inflammation, resulting in the left side of the back radioactive pain symptoms, can also involve the left upper limb, neck pain, activity restrictions are also more obvious. Third, back trauma, acute strain of the back muscles can occur in the process of exercise, the muscles will have obvious swelling and pain symptoms.