> Dogma: We must drink water in order to prevent heat illness during exercise in hot conditions.

> Science: There is no relationship between fluid intake and hydration, and the incidence of heat exhaustion or heatstroke. The only correlate to core temperature is running pace.

If I'm reading it correctly, there's no relationship between (fluid intake and hydration), and (the incidence of heat exhaustion or heat stroke).

It's a shame English isn't associative.