[Google Translated from German] Acute fatigue and exhaustion after successfully completing a sporting or professional challenge are not unpleasant per se. However, some people feel tired and underperformed in the long term. Fatigue is one of the most common complaints in the population. In 1869, George Beard, USA, described a clinical picture that is still relevant today [1]: "Neurasthenia" corresponds to the symptoms of the somatoform disorders of our time. Jean M. Charcot rated the symptoms as a functional disorder of the CNS, while Sigmund Freud rated it as a conversion neurosis [2]. Textbooks from the 19th century contain the symptoms that are still present today, such as being easily exhausted, having trouble concentrating, headaches, dizziness and irritability. Binswanger wrote a monograph on "The Pathology and Therapy of Neurasthenia" with a description of symptoms that corresponds to today's Chronic Fatigue Syndrome (CFS) [3]. Initially, neurasthenia was usually regarded as a physical illness. It acquired an increasingly spiritual component after the diseases that were common at the time, such as tuberculosis or lues, which led to exhaustion, increasingly receded into the background. In contrast, in the USA and England between 1934 and 1957, several diseases were described that were accompanied by acute general weakness and slight fever, but without neurological deficits. At that time, "atypical poliomyelitis" was discussed, since poliomyelitis was the focus of attention at that time. Similar symptoms of the disease occurred between 1950 and 1980, in some cases epidemically, which coined the term "benign epidemic myalgic encephalomyelitis". Rest, in German, available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10169290/
He calls graded exercise therapy "pacing". I also looked at reference 3. The descriptions of a patient sounded more like POTS or a form of OI to me, as typical symptoms of OI like chest pain and cognitive impairment ("empty headedness") are mentioned as arising from short walks.
