Which is in itself odd, as there's no obvious mechanism (at least in a developed nation inhabitant who typically have considerable fat reserves and ready availability of food) for the immune system to need resources which would be otherwise used by the muscles.
Like we can all feel the lack of "energy", but that energy isn't the same thing as actual calories, glycogen, blood O2 and so on. Presumably a lot of CFS conditions are relating to that biological switch - "you're ill, rest up!" - getting stuck in the "on" position, but AFAIK nobody has definitively found it despite a whole lot of looking.
Like we can all feel the lack of "energy", but that energy isn't the same thing as actual calories, glycogen, blood O2 and so on. Presumably a lot of CFS conditions are relating to that biological switch - "you're ill, rest up!" - getting stuck in the "on" position, but AFAIK nobody has definitively found it despite a whole lot of looking.