There are a number of causes of pain on the left side of a woman’s back, such as too much activity, insufficient blood supply to the heart, and periarthritis of the shoulder. 1. Excessive activity: If you usually often lift heavy objects, muscle strain caused by excessive activity, it may also be due to muscle strain caused by a long-term posture, such as stooping, sedentary, leaning forward, squatting, etc., all of which can cause back pain. 2. Insufficient blood supply to the heart: after excessive fatigue, exertion, emotional upset caused by myocardial ischemia, there will be pain in the anterior region of the heart, so there will be pain in the back, and there will even be panic and sweating, which will cause back pain. 3. Periarthritis of the shoulder joint: due to the long time chronic strain, there will be a feeling of back pain, upper limb activity is limited, soreness and numbness, you can properly carry out shoulder joint exercise to relieve pain. If the symptoms are not relieved, it is recommended to go to the hospital in time to do the examination and cooperate with the treatment.