Dietary sources of electrolytes
Many sports drinks, bars, tablets and gels are formulated with electrolytes to help you replace those lost during exercise. The Standard American diet includes about 6-9grams of sodium intake per day. Basically 1 glass of orange or tomato juice can replace all the potassium, magnesium, and calcium lost in 2-3 liters of sweat. Sodium is readily found in tomato juice, soups, salt added foods, or you can add ½ tsp table salt per liter of water. Potassium is abundant in both orange juice and bananas.
Eight practical recommendations
1) Use electrolytes with your water when hydrating. Hydrating solely with water leads to water intoxication and an electrolyte imbalance.
2) Acclimate to heat by exercising in heat
3) Test different levels of electrolytes during training in heat
4) Weigh yourself prior to a long exercise bout in heat and again afterwards. Subtract the total fluids you took in and the difference will be your hydration deficit. Rehydrate with 150% of your fluid losses (at approximately.68L fluid/lb lost or 2L of fluid to replace a 3 lb loss).
5) Do not make any drastic changes to your diet for the days leading up to the race and on race day. Drastic changes can adversely affect your electrolyte balance.
6) During races in extreme heat, consider cooling your head, neck at aid stations where ice is available. Not only does this feel good, it allows the oxygen carrying blood to concentrate on the working muscles, which in turn improves your exercise capacity.
7) Make sure your recovery drink or meal contain adequate levels of all 5 electrolytes. This comparison review looks at the electrolyte levels of the leading recovery drinks on the market http://www.firstendurance.com/research.html
Acceptable ranges for electrolytes in a recovery drink
Magnesium: 200-800 mg
*Excess potassium can become problematic (see potassium above)