Hydration and fluid replacement is critical to athletic performance (1). I’m not talking about your walk in the local park, but intensive activities that last longer than 1 hour. I hear many theories on how much water one should drink during sporting events and many are “one size fits all” in nature. Intense activities lasting longer than an hour will require a specific re-hydration strategy. This applies for both hot and cold environments. It is clear that starting your exercise session dehydrated is one of the leading causes of heat-related illness.