That is not supported by the article.
"Even if hardcore exercisers do have more calcium buildup, it’s still not clear if that’s damaging the heart..."
The article states calcium build up in the heart is a bad sign for sedentary people and that it is not clear what it means for healthy people.
There are similar syndromes/symptoms that mean different things for people with different activity levels - folks who do aerobic exercise a lot have larger hearts than sedentary people, the enlarged heart can be a symptom of very serious problems - but mostly for sedentary people.
"Even if hardcore exercisers do have more calcium buildup, it’s still not clear if that’s damaging the heart..."
First, I'd argue that an hour a day is not "hardcore". Anyone trying to lose weight can easily fall in this category, including me currently. Second, the actual underlying study upon which this article is based seems to indicate that calcium buildup is bad for everyone. Time Magazine went out and found someone who gave a quote contradicting the study, but that was the whole point of my comment.
Different studies and individual researchers have different views on all of this stuff. Some say that lots of exercise is bad, and others say it is great. The point is that nobody knows, but everyone seems to be be publishing studies advocating for a given position.
There are similar syndromes/symptoms that mean different things for people with different activity levels - folks who do aerobic exercise a lot have larger hearts than sedentary people, the enlarged heart can be a symptom of very serious problems - but mostly for sedentary people.