The human body is a weird and amazing machine. It's easy to forget this, alone in the complacency and familiarity of one's own form and rhythms. But then one remembers the existence of runners with the mental and physical stamina to run a hundred miles or more at a stretch and soon the potential of the familiar starts to seem a lot more promising.
Post-race, the blood of a marathoner can paint a picture of diseased organs and biochemical decay.
(Getty Images)
But such feats are...