I am a former endurance athlete with heart disease unrelated to sport. I had a heart attack at age 43 which left me with permanent heart damage. Almost 3 years ago, I had quadruple bypass which restored good blood flow to my heart but, of course, had no effect on the damaged muscle. So, my ejection fraction is 41%, which is slightly above congestive heart failure levels. It was 41% before surgery, 41% after surgery, and 41% after 1,000 miles of cycling. I'm 66 and at an "ideal" weight.

Here's the thing: I have learned to "train" smart - lots of base miles before I hit the hills or the intervals, and at least 2 days of rest a week. Also, strength training to keep the bones strong, increase comfort on the bike, and more short interval power. This year I'm on track to ride over 2,000 miles with about 36,000 ft. of climbing...maybe more. I'm entering a 50 mile gravel race in October and can't wait! I feel great and love my longer rides.

I agree that these associations between endurance sports and AF apply to very long efforts at threshold, not short intense intervals, and the mileages most of us ride are clearly not hurting us and helping us in so many ways!