hello!
my (perhaps flawed) logic tells me that too much of anything is bad.
i believe exercise is often very healthy,
but running marathons might be a bit too much exercise.
i doubt the human body has evolved to be fit enough to train everyday so you could run marathons.
especially when you're already 64 and having heart (rhythm) problems,
it might be a good idea to slow down.
my apologies if i just gave bad advice.
good luck!
Well, I didn't get any responses here, but from googling around on the web I came to the conclusion that diltiazem, a calcium channel blocker, would be better for an athlete than atenolol, a beta blocker. So I called the doctor who agreed to change my medication. Yesterday on the treadmill, after having only taken one 25mg dose of atenolol my heart rate only showed a bit over 120 when I was doing a pace for which a 140 should have been called for. I'll find out later today on my 11 mile run how diltiazem treats me.
I should add that the doctor. said the reason for the racing heart rate was a leaky valve. Sorry to post in a new message, but I couldn't see any way to edit the original.