[albie]

Heart attack most likely. Happened to Jim Fixx. Runners have hearts that are rock hard. There’s little capacity for blood. That’s why long distance running is so bad for you. Any sudden jolt, scare or movement that would require a quick rush of blood can kill.

[RoosterRedux]

And IIRC Fixx had a family history of heart problems and before he began running was overweight and a two pack a day smoker.

[oh8eleven]

Runners have hearts that are rock hard. There’s little capacity for blood. That’s why long distance running is so bad for you.
One of the most ignorant posts I've ever seen on FR.

[Dick Vomer]

Heart attack most likely. Happened to Jim Fixx. Runners have hearts that are rock hard. There’s little capacity for blood. That’s why long distance running is so bad for you. Any sudden jolt, scare or movement that would require a quick rush of blood can kill.huh? "Rock hard" hearts. This is an April Fool post, right?

[JimRed]

Runners have hearts that are rock hard. There’s little capacity for blood. That’s why long distance running is so bad for you.

Not correct. Distance running (or other similar aerobic training) over a period of time causes the heart to grow additional branches to arteries and capillaries to better serve the muscle.

When I had my heart attack last year they told me that the difference between life and death was probably the extra circulation built up over those years. Irritated linings in the arteries and plaque sticking to it are the usual problem.