This is a pain disorder that is chronic. With this disorder, pressure applied on points that are sensitive in one muscle, also known as trigger points, can cause pain in other parts of the body that are seemingly unrelated. This is known as referred pain. This occurs most often when there has been repetitive contraction of a muscle. Jobs and hobbies that cause motions that are repetitive and muscle tension that is stress-relation can also cause this condition.
Myofascial Pain Syndrome Joseph Smith, PhD