The natural choice for hydration is water. It hydrates better than any other liquid, both before and during exercise. Water tends to be less expensive and more available than any other drink. You need to drink 4-6 ounces of water for every 15-20 minutes of exercise. That can add up to a lot of water! Athletes who don't consume electrolytes under these conditions risk overhydration (or hyponatremia). The most likely occurence is found in the longer events (five hours or more) when athletes drink excessive amounts of electrolyte free water, and develop hyponatremia (low blood sodium concentration).
Performance drinks can be helpful to athletes who are exercising at a high intensity for 90 minutes or more. Fluids supplying 60 to 100 calories per 8 ounces helps to supply the needed calories required for continuous performance. It's really not necessary to replace losses of sodium, potassium and other electrolytes during exercise since you're unlikely to deplete your body's stores of these minerals during normal training. If, however, you find yourself exercising in extreme conditions over 5 or 6 hours (an Ironman or ultramarathon, for example) you will need to add a complex health drink with electrolytes.
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