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Sensitive areas of tight muscle fibers can form in your muscles after injuries or overuse. These sensitive areas are called trigger points. A trigger point in a muscle can cause strain and pain throughout the muscle. When this pain persists and worsens, doctors call it myofascial pain syndrome. 1  Symptoms.
In most cases, upper and middle back pain is caused by: Overuse, muscle strain, or injury to the muscles, ligaments, and discs that support your spine. Poor posture. Myofascial painMyofascial pain that affects the connective tissue of a muscle or group of muscles. For example, some people hurt their backs when they: Slump or slouch when they sit or stand.