Kirk Johnson, To the Edge: A Man, Death Valley, and the Mystery of Endurance, Warner 2001, p. 179:
Runners, I believe, are the last great Calvinists. We all believe, on some level, that success or failure in a race — and thus in life — is a measure of our moral fiber. Part of that feeling is driven by the psychology of training, which says that success only comes from the hardest possible work output, and that failure is delivered unto those who didn't sweat that extra mile or that extra hour. The basic core of truth in that harsh equation is also one of the more appealing things about recreational racing: It really does equalize everyone out. A rich man's wallet only weighs him down when he's running, and a poor man can beat him. Hard work matters.
In one way running equalizes, in another it doesn't.
It levels the disparities of class and status and income. You may be a neurosurgeon or a shipping clerk. You won't be asked and no one cares. The road to Boston or Mt Whitney is no cocktail party; masks fall away. One does not run to schmooze. This is not golf. Indigent half-naked animal meets indigent half-naked animal in common pursuit of a common goal: to complete the self-assigned task with honor, to battle the hebetude of the flesh, to find the best that is in one, the 'personal best.'
But in quest of one's 'personal best' the hierarchy of nature reasserts herself. We are not equal in empirical fact and the road race makes this plain. In running as in chess there is no bullshit: result and rank are clear for all to see. Patzer and plodder cannot hide who they are and where they stand — or fall.
So although running flattens the socioeconomic distinctions, it does so only to throw into relief the differences of animal prowess and the differences in spiritual commitment to its development.