[WalterBright]

I read that doing a marathon without proper and protracted training is very hard on the heart, so you may have been pushing too hard.

[jimhefferon]

I do the standard training, starting from 20m/w at the new year, and running on Memorial Day. (I follow Amby Burfoot's excellent plan.)

Certainly my story is anecdotal. But I guess I'm just saying that while bodies are amazing, sometimes they are amazingly frail.