Pre-Exercise Nutrition
Ellen Coleman, RD, MA, MPH © 2004

Triathletes often train or compete in the morning without eating. This overnight fast lowers your liver glycogen stores (the source of blood glucose) and can cause fatigue during exercise. Eating a high carbohydrate power breakfast before morning exercise will maintain blood glucose levels so that you can perform at your best.

During exercise, you rely primarily on your pre-existing glycogen and fat stores. Although breakfast doesn't contribute immediate energy, it can provide energy when you exercise for longer than an hour. The carbohydrate in the meal elevates your blood glucose to provide energy for the exercising muscles. It can also keep you from feeling hungry, which in itself may impair performance.

You should consume your breakfast one to four hours before training or competition, to allow adequate time for the food to empty from your stomach. Exercising with a nearly full stomach can cause indigestion, nausea, and vomiting as blood is diverted from the stomach to the muscles.

The amount to consume depends on the timing of the meal. To avoid potential gastrointestinal distress, the carbohydrate and calorie content of the meal should be reduced the closer to exercise the meal is consumed. For example, you can consume a large meal of 700 to 800 calories four hours before exercise, while a smaller meal of 300 to 400 calories is better an hour before exercise.

Consuming carbohydrate several hours prior to morning exercise helps to restore your liver glycogen stores, which will aid endurance events that rely heavily on blood glucose. If your muscle glycogen levels are also low, consuming carbohydrate several hours before exercise can help to increase them as well. If stomach emptying is a concern, you can use liquid meals.

Next: "Part 2"