There are three main reasons for pain in the middle of the back shoulder: First, strain or injury of the supraspinatus muscle in the upper side of the back shoulder, usually due to excessive force in abduction, which leads to strains due to intense muscle contraction, or frequent abduction activities, which leads to strain due to fatigue of the muscle, will form aseptic inflammatory lesions, which can cause pain due to stimulation of the peripheral nerves. Second, due to the strain or strain injury to the infraspinatus and teres minor muscles, for example, when the shoulder joint is externally rotated due to the relative weakness of the muscle strength, if the external rotation force is too large, it may lead to strain injury, and frequent movements will lead to strain injury, which will cause obvious pain. Third, due to the trapezius muscle of the back shoulder position strain, this situation is mainly due to the head down for too long, bilateral elbow joints without support, resulting in the continuous tension and fatigue of this muscle, there will be pain.