I don’t disagree that regular exercise is very healthy and needed by the body.
The exercise requirements and exercise limits for the young and old are different.
I can’t say that I understand the heart issues well—except that I was told about the downside to iron man by a heart surgeon for atrial fibrillation who said he saw aging iron men in their 50’s in his office regularly for ablations that are designed with some success to stop atrial fibrillation.
Yes, atrial fibrillation (AF) is much discussed in the linked article.
—”Does the scientific community have a solid definition for what an endurance athlete is? How many hours it takes per week or month to go from part-time participant to all-out endurance junkie? “Hell no,” said Dr. John Mandrola, a heart-rhythm doctor from Louisville, Kentucky, who takes a keen interest in the hearts of endurance athletes, and who is himself a cyclist with atrial fibrillation (AF). “What’s too much? That’s the $64,000 question. Though I will say it’s a little like what the judge said about indecency: ‘I know it when I see it.’”