Muscle abnormalities worsen after post-exertional malaise in long COVID, 2023/4, Wüst, van Vugt, Appelman et al

I did a kind of experiment on myself while I had about 5 weeks of post-COVID symptoms (mostly cognitive issues + light sensitivity + fatigue, feeling like I needed to turn it in for the day by 1 pm). I had regular exposure to cognitive exertion by trying to work intensively as normal - I always recovered from it come the next morning. I tried vigorous cardio on an exercise bike for about 30 minutes, one time early in the day before I was wiped out and once late in the day after I was wiped out. Both times, I got very dizzy and cognitively useless and woke up still feeling the same for all of the following day, but much more strongly in the latter case where I was already cognitively exhausted before exercising. Felt like it transported me a fortnight backwards. I had no muscle pain or weakness in any of these scenarios.

So yes, my experience with a kind of PEM was definitely exercise-induced and not cognitively-induced. Just another anecdote and I am sure others may have different experiences and I do not wish to minimise those.

Sidenote (speaking of anecdotes) at another time I was disabled for nearly a year with effectively no physical activity and very minimised manual activity around the house. I had objective deconditioning evident from hand-grip strength tests recorded over time and undertaken by an unbiased professional. I had zero ME/CFS / LC -esque symptoms associated with my deconditioning .

So in my experience, empirical muscle deconditioning had no relationship to ME etc as I understand it (as we would expect, not being BPS people), while exercise, specifically, strongly induced something like PEM during a nasty post-COVID period.