Abstract
Fibromyalgia is characterized by diffuse pain, the origin of which remains obscure. This study explored a phenomenon labeled Diffuse Muscle Coactivation (DMC) as a possible source of pain in fibromyalgia. DMC is defined as an increase from resting levels (tonus) in the electrical activity of any muscle during a movement which does not involve that muscle and is not part of the agonist-antagonist unit. When compared to controls this activity in persons with fibromyalgia was 1.75 times more prevalent and demonstrated significantly higher peak amplitudes. Possible neurological mechanisms are discussed.