I'm 65 and still actively employed in police work. I mostly ride my bike, but I have a bowflex machine to keep a little resistance exercise in the mix.
Since I had a little roto-rooter job and some stents in the old ticker a few years ago, I've been advised not to push the heart-rate much past the "aerobic training range", but I have not had any problems since the stents.
Just as a matter of terminology, I much prefer the older "aerobic" to the newer "cardio". I don't know when the terms morphed, but aerobic implies the involvement of the entire cardiovascular system which is in fact the goal.
"cardio" sounds to me like trying to isolate the heart, which is just the pump, after all.
Likely an individual quirk.....