Water and Exercise

by Dr. Greg DeLaurier

Water comprises approximately 60% of our body weight. This water is present in our bloodstream, in the microscopic cells of our organs, and between these cells. Water is essential for the proper function of all our body parts and is especially useful in carrying blood cells to all our systems. The blood cells transport oxygen to organs such as muscle which are necessary for exercise (i.e. karate).

When we exercise, our muscles produce heat, increasing temperature. Sweating corrects this increase in temperature by evaporation on our skin. This is a major source of water loss during exercise. Other places that we lose water is through our kidneys and in the air we breathe out.

Small losses in the overall volume of water in our system that occur during exercise can affect exercise performance resulting in less power and endurance. It is important that this water loss is replaced before, after, and even during prolonged activity.

One of the most common symptoms of dehydration is fatigue. Other signs are dizziness, headache, nausea, and obviously, thirst. In vigorous exercise, fainting and even seizures may occur.

In activities lasting less than 1 hour, water is the best replacement. Generally speaking, an average adult should drink 1 cup of water for every 15 minutes of moderate exercise. After the activity, drink additional water beyond the sensation of thirst. We should avoid colas and other caffeinated beverages since they promote too much water loss through the kidneys (diuresis).

In more prolonged exercise, dilute carbohydrate solutions may help replace lost glucose in our body. However, solutions containing more than 10% carbohydrate slow the emptying of the stomach, producing nausea. For most people, water may still be the best replacement fluid. Whatever you do, just don?t let Mr. Gomez find out you had sweet tea before training.

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