The pain in the upper part of the back may be caused by the following reasons: 1. The mattress or bed board may be too soft or too hard to sleep on, resulting in the muscles of the back needing to exert themselves for a long time to maintain a certain posture when sleeping, resulting in local muscle strain pain, usually get up and move around, the symptoms will naturally ease after the local muscles relax. 2. It is common for people who have been doing back exercise or heavy physical labor for a long time to develop back muscle strain or back fasciitis. 3. It may be a misalignment of the small joints in the back, usually the painful area is in the middle of the upper thoracic vertebrae, and there is a clear pressure point and a limitation of the movement of the thoracic vertebrae.