Upper trapezius strains often are characterized by a constant, radiating pain throughout the neck and shoulders, particularly the area between the shoulder blades. Often, these symptoms subside during rest, but in some cases, the pain may continue even when the affected muscles are immobile. In such cases, the pain may disrupt sleep, largely due to compression of the shoulder muscles when a person sleeps in certain positions. During the day, pain may worsen as a result of certain activities or, in many cases, bad posture. This is particularly evident in people who work at a desk or computer because they often sit in a hunched or slouched position. At the time of injury, the pain may be accompanied by a heat sensation caused by inflammation of the muscles and tendons in the region. The person may also experience a warm, tingling feeling in the shoulder area. In some cases, the pain radiates down the arm. If the strain is severe enough, swelling may be visible at the injury site, and may make the surface of the skin feel warm to the touch. This injury can prevent people from performing daily activities as it makes it difficult to extend the arm or lift heavy objects. It also can cause headaches at the base of the skull that sometimes extend into the neck.