Many people run not to lose weight but to loosen the chains of a mechanized culture, not to postpone death but to savor life. For those runners, the admonitions of critics who warn against the dangers of the sport are moot; they run quite consciously, as informed, consenting adults, to exceed their previous limits and to press the edges of the possible, whether this means completing their first circuit of a four-hundred-meter track without walking, or fighting for victory in a triathlon,
