> Just want to point out that there's a difference between "pain" and "discomfort". You are redefining words to make an argument. Endurance athletes, in partic

> Just want to point out that there's a difference between "pain" and "discomfort". You are redefining words to make an argument. Endurance athletes, in particular, will most certainly experience various pain sensations in the course of normal training or an event. Body awareness is another matter: an elite athlete (presently or potential) is usually better able to interpret what their body is signaling - including noticing when something is going wrong. Edit: And, actually, sometimes a real injury manifests itself as a discomfort during exercise, not pain. … For what it is worth, you can become dehydrated enough to compromise performance in an hour, less if it is very warm. Dehydration to the point of needing medical attention can occur in 2-3 hours at a moderate intensity. Typical symptom of mild dehydration (the kind you can suffer sleeping on a hot night) is discomfort in the form of a headache.