Key points: * Fatigue during prolonged heavy exercise is often associated with low or depleted muscle glycogen stores and with lowered blood glucose. * Eating a high-carbohydrate meal 2-4 h before constant-pace exercise can improve endurance capacity (time to exhaustion) but may not be advantageous in time-trials, especially if sports drinks are consumed during the trials. * Contrary to earlier reports, there appear to be no adverse effects on endurance capacity of consuming well-formulated carbohydrate solutions within the hour before exercise. Practical Tips: * About 3-4 hours before exercise, eat an easy-to-digest high-carbohydrate meal that provides about 2-2.5 g of carbohydrate/kg body weight. * About 1-2 hours before exercise, ingest 300-600 ml (10-20 oz) of water or a sports drink to ensure that you are well hydrated before exercise. Consumption of a sports drink is a way to provide hydration and extra carbohydrates. * Drink a sports beverage frequently throughout prolonged exercise, following the simple rule that you should drink enough during exercise so that you do not gain or lose body weight during the exercise period.
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