Objective Evidence of Post-exertional “Malaise” in Myalgic Encephalomyelitis and Chronic Fatigue Syndrome

Abstract

Essential elements of Myalgic Encephalomyelitis (ME) are muscle (weakness) and tenderness, cognitive deficits, neurological impairments, especially of cognitive, autonomic and sensory functions, but above all, post-exertional“malaise”: a prolonged increase of symptoms after a minor physical and mental exertion. Chronic fatigue Syndrome (CFS) is defined as clinically evaluated, unexplained (persistent or relapsing) chronic fatigue, accompanied by at least four out of eight specific symptoms, e.g., sore throat, unrefreshing sleep, and headaches. Since cognitive deficits and post-exertional “malaise” are not mandatory for the diagnosis CFS, only part of the CFS patient group meets the diagnostic criteria for ME. So, post-exertional “malaise” is considered to be the distinctive feature of ME. However, “malaise” is an ambiguous and subjective notion. In order to assess post-exertional malaise objectively, several studies have employed widely used methods to quantify the deviant effects of exertion in ME (CFS). This review focuses on the long-lasting (negative) effects of exercise on the performance indicators of the physical exercise capacity, the cognitive deficits and the muscle power.