I don't really know, but the fatigue that is felt is not due to exertion or a previous medical problem.
Mostly the fatigue that is not warranted or due to strenuous ongoing exertion
My friend was just diagnosed with Chronic Fatigue Syndrome but I don't know much about it. It's characterized by long term fatigue and other symptoms, and it severely limits a person's ability to live a normal life. What are the other symptoms?
The fatigue is not due to strenuous ongoing exertion, is not much relieved by rest, and is not due to a previous medical condition. Fatigue is a common symptom in many illnesses, but the unexplained fatigue and severity of functional impairment in CFS is comparatively rare.