Carbohydrate is the most important fuel during exercise. The storage form of carbohydrate in the body is glycogen and is found in the muscle and the liver. Muscle glycogen contains about 300 to 400 grams of stored carbohydrate, which is equivalent to 1200 to 1600 calories worth of energy. Training increases the glycogen stores in the exercising muscle, which is a physiological adaptation of training. In order to utilize glycogen as an energy source during exercise, the diet must contain adequate amounts of carbohydrate to replenish the glycogen used during exercise. Ingesting carbohydrates before and during exercise spares muscle glycogen, enabling us to exercise longer before the inevitable fatigue sets in. Consuming adequate amounts of carbohydrates after exercise is also vital for recovery from exercise.

The following is a list of guidelines for carbohydrate consumption before, during, and after exercise. Following these may help you feel more energetic during your training and help you meet your training and racing goals.

1. If you are training or competing in the morning, try to consume at least 30 grams of carbohydrate before your event. While we sleep, the body uses stored liver glycogen as an energy source. Thus, when we wake up our glycogen capacity is diminished. A carbohydrate-filled breakfast will further spare muscle glycogen and enable us to maximize our energy stores available.

2. During an endurance event, try to consume at least three cups of a glucose replacement beverage every hour. This provides an energy source as well as a fluid source. The optimal beverage is a six percent carbohydrate-electrolyte solution containing a combination of fructose and sucrose. (Gatorade is six percent, Exceed is seven percent, and PowerAde is eight percent).

3. Exercise gels can also be used as a glucose source during endurance events. It is vital that one cup of water be consumed along with each packet of gel. If not, the glucose will not be absorbed as quickly from the gut and will not be immediately used during exercise. Insufficient fluid intake with the gels can also cause cramping, which is obviously undesirable during exercise.

4. Immediately after exercise, muscle glycogen stores are like sponges: they rapidly absorb dietary carbohydrate. This will enable us to more quickly replace the glycogen we used during exercise. For optimal repletion, consume one gram of dietary carbohydrate per kilogram of body weight within forty- five minutes of completing the exercise.

5. If we are anxious or stressed (before a race!), the body secretes the hormones epinephrine and norepinephrine. These hormones break down liver glycogen stores, thus diminishing our total energy available. This effect may deplete muscle glycogen stores sooner and may cause us to fatigue earlier during exercise. Try to remain as calm as possible before a race or training event to maximize the energy stores available for exercise.

Denise Feeley is an avid runner and Registered Dietitian with more than seven years of experience counseling athletes. She is currently an adjunct professor in the Department of Exercise Science at George Washington University. She is available for nutrition counseling. For information or questions contact her at denf44@yahoo.com.