Yes, both ways regarding the heart, as in doing too much and too little.Likewise, and I've gotten significantly weaker and de-toned.
As a former fitness enthusiast to ward off 'stress' (that term which 'everyone' finds nebulous for now),
I find this scary - the heart is THE large muscle that needs lots of exercise if one is to carry on... .
The lack of 'something' in the muscles, I think, has put my heart and lungs under a lot of strain. Do you feel it at all? I feel it when I hang clothes on the line for instance, it's hard work.