Interesting, given that I was down in Copper Canyons just a few weeks ago to run the Caballo Blanco race. I don't see Micah True as establishing anything. Yes

Interesting, given that I was down in Copper Canyons just a few weeks ago to run the Caballo Blanco race. I don't see Micah True as establishing anything. Yes, it's likely he died of cardiac arrest. Yes, he displayed the enlarged left ventricle characteristic of people who run a lot. But as far as I'm aware, his family history is unknown. It could be that he died of a genetic (inherited) disorder and that he actually lived longer, delayed his heart attack, _because_ he was a runner. (This is the likely situation with Jim Fixx, a famous guy back in the 80's who promoted the health benefits of running, but then died of a heart attack: https://en.wikipedia.org/wiki/Jim_Fixx#Death https://en.wikipedia.org/wiki/Jim_Fixx#Death ) One current conjecture in medical science is that enlarged left ventricle and scarring increases likelihood of cardiac event; at this point I'm pretty sure it remains mere conjecture. Regarding marathons: what would you expect to be leading cause of death in marathons? Surely not cancer. Running a marathon stresses your heart. If you have genetic cardiac issues (which many do) it's more likely that they will appear in a marathon than when you're walking down the street. It's a huge leap to suggest that training for a marathon increases overall risk of heart failure. It could just as easily be that the marathoner has actually extended his/her life by running, that they would have died earlier if they hadn't kept their diseased heart as healthy as it could be by doing lots of running. As far as I'm aware, there's no science out there that establishes that marathoning causes people to die earlier than they otherwise would, and lots of evidence to the contrary.