Interesting read. Drink only when you're thirsty, bag the electrolytes.
Summary:
http://www.irunfar.com/2012/07/waterlogged-a-dogma-shattering-book.html
Summary:
- Fluid (and weight) loss during endurance exercise is normal, if not optimal.
- There is no relationship between fluid intake and hydration, and the incidence of heat exhaustion or heatstroke. The only correlate to core temperature is level of exertion.
- The body self-regulates blood sodium concentration via several mechanisms, including sodium sparing in sweat and urine. When one drinks to thirst, blood sodium concentration invariably rises during prolonged exercise; it never falls.
- The self-regulation of sodium concentration results in sodium excesses being secreted; salty secretions will cease when sodium balance is achieved.
- There is no scientific evidence that shows sodium (or other electrolyte) deficits in those with muscle cramping.
http://www.irunfar.com/2012/07/waterlogged-a-dogma-shattering-book.html