A research abstract from the Journal of sports Medicine May 15 05 showed a 28% incidence of hyponatremia (a condition where the salt concentration is too low) in runners at the Houston Marathon. Studies, done at other events yeilded similar results. Their conclusion is that you can definitely over hydrate. Females tend to hydrate more than men. (My advice is to experiment with hydration levels in all weather conditions and know what your body needs). Temperature and perspiration rate should figure in to the equation of how much to hydrate. Female, low body wieght, high fluid intake deviod of electrolytes, anti inflamatory consumption within 24 nours, high teperature/ high humidity are the predominant risk factors. Br J Sports Med. 2006 Feb concludes that fluid intake should match perspiration output and should be adjusted for the amount of salt in the sweat.
My take on this: Electrolyte drinks do help!