> My heart rate has never gone back to where it was and my breathing never returned to being fully "satiating". > Gone through the gamut of medical tests and everything is "normal".

This, 100% this; and it's a concept that's really hard to get across to people, even doctors.

I got to the point where I decided to start doing stuff again because it was the only way to get back. I'm in way better shape that previously since covid, but that "fully satiating breath" is still not coming.