Much has been written about the issues of what is the point beyond which exercise is no longer health promoting but rather damaging to the heart or is there a point.
Larry Creswell writing on his blog Athlete's Heart Blog reviews a recent article that studied 33 endurance athletes with a history of prolonged intensive aerobic training. These guys trained so long and so hard that you might think that surely what they did would approach that limit and have evidence of cardiac damage. Yet that was not the case. (Dr. Creswell'sl blog continues to be a great source for issues involving what the blog title suggests.)
The data are interesting but finding 33 white swans does not rule out the existence of black ones.The fact that these athletes continued to be able to exercise at a prodigiously high level suggested that that did not develop some serious heart problem. Is there a survivor bias at play here?
addendum 0ct 21 2017.Typo in headline corrected.