Well I could reasonably bike up one specific very steep hill near my place without downshifting much until I got covid.

Then it took me more then half a year to get back to that point. It was a very slow recovery but most importantly, it could be quantitatively measured first from how far until I had to disembark my bike to walk up the rest of the hill to eventually the lowest gear I had to to shift into to get to the top without ever disembarking.

I’ve never had any other flu-like sickness cause me to be weak for so long.