Cycling in the Front Range hills was definitely more difficult after my COVID infection last spring. It took two full months to feel "normal" again. But I only felt the recovery time when on the bike--all other activities felt fine within a week after acute symptoms. Those were mild--I was very surprised to get a positive antigen test result afterwards, just a precaution before joining friends for an indoor event.
Breathing and heart rate weren't alarming during recovery. I just didn't feel much energy, so I cycled slowly. I don't have monitors, and don't have any baseline data, just empirical observation.