Muscle activity and chronic muscle pain

Objectives: Firstly, to review studies on chronic muscle pain, including fibromyalgia [FMS], which show changes in certain muscles that could evoke muscle pain during muscle activity. Secondly, to discuss the relation between localized muscle pain and FMS. Findings: In shoulder myalgia and FMS there are changes in certain muscles. e.g., in the trapezius muscle, indicating disturbances in microcirculation. Two studies show reduced levels of adenosine triphosphate in muscles at rest in FMS. Conclusions: A disturbed microcirculation, in combination with muscle activity, could induce localized muscle pain. In patients with chronic localized pain and in those with FMS, where the generalized pain is preceded by localized pain, the muscular changes may initiate and maintain the sensitization of second order nociceptive nerve cells, which is a key finding in both chronic regional muscle pain and in FMS.