CFS and FMS are generally considered to be one and the same and the symptoms are varied. The primary symptom of fibromyalgia is systemic pain. The entire body aches. Because there is so much pain associated with movement and muscles, it was originally thought that FMS involved an inflammation of the fascia and the fibrous tissues. That would be the ligaments, the tendons, muscles and the sheath of fascia that contain the entire system.
Current understanding is that there is no inflammation present.
But though pain is the most pervasive symptom, there is more. Sufferers of FMS invariably are poor sleepers. The lack of sleep makes the symptoms even more intolerable and the symptoms make sleeping difficult. Research points out that insomnia is actually part of the syndrome, not merely present because of the pain associated with it. People with FMS have a disrupted circadian cycle, the natural process that tells our body when to sleep.