In reply to wbo: And I think I should add to that that I've never heard that it was anything except moaning/jealousy.
As a comment, you will sometimes see sports scientists and psychologists talkabout the thin margins between success and failure. Then go and look at, and think about, Salazar's 'Duel in the Sun' Boston with Dick Beardsley, and think about the impact that that sort of ability to push/damage yourself can have. I cannot imagine pushing myself in a single race so hard that it permanantly damages my health.