Optimal Beverages to Consume while Exercising in the Heat or for Greater than One Hour

Hot and/or humid environments increase both your sweat losses and your sweat rate.  Consequently, there are two exceptions to the guideline mentioned above that water is adequate for exercise lasing less than one hour.  If you are exercising in the heat or exercising for more than two hours, you need to consume sodium and chloride because these electrolytes are found in the greatest concentrations in sweat.  (McArdle et al., Sports & Exercise Nutrition, 2005).  Thus, drinking a sports drink containing soduim chloride is beneficial under these two conditions because sodium stimulates both thirst and fluid retention.  It also helps to prevent “hyperhydration.”  Excessive water intake can result in a life-threatening condition known as hyponatremia or hyperhydration.  You can drink too much if you exercise in the heat for more than one hour or exercise continuously for more than two hours and consume only water with no added electrolytes.  Drinking too much water, beer or other low-sodium fluid can quickly dilute the blood (plasma) sodium concentration. When this occurs, the osmotic balance across the blood-brain barrier is disrupted and water quickly enters the brain, causing swelling that can lead to seizures, coma, & even death.  The recommendation when exercising in the heat or during exercise lasting more than two hours it to either: 1) drink water plus a sports drink or, 2) drink water and consume food containing sodium.  Your goal is to drink enough to replace your losses without drinking excessively (you do not want a “sloshing” stomach). 

Most sports drinks contain 6% to 8% carbohydrate – the ideal carbohydrate concentration for your body when exercising.  The advantages of drinking a sports drink containing 6% to 8% carbohydrate are:

1)     Maintains glucose (energy) metabolism.  Select sports drink that contains both glucose and fructose for a greater benefit. 

2)     Preserves glycogen (stored energy) during prolonged exercise.

3)     As recovery drink, improves endurance capacity for additional exercise.

First published in The Mystic, Stonington and Lyme Times in March 2013.