During the training phase, maintaining Caloric balance (eating enough Calories to replace those used during the day's exercise) is the biggest challenge faced by endurance athletes. Not only will daily Caloric requirements be significantly beyond normal dietary intake, the time available to eat (including snacks) is reduced by the time requirements of the training itself. This is particularly true with swimming and running as snacking while exercising is almost impossible. To avoid slowly losing ground nutritionally, you will need to closely monitor your daily Caloric expenditures, make a conscious attempt to snack throughout the day to replace thoise Calories, take advantage of the post exercise glycogen replacement window to restock muscle glycogen stores for the next day's training, and weight yourself daily to be sure you are staying in "Caloric balance".

How about the triathlon itself? Nutrition during the pre-event interval (4 days, 4 hours, 4 minutes) is essentially the same as for all other competitive events. The body can store only so much glycogen in the muscles and liver during the 4 days before the competition, and the digestive tract can handle only so much volume in the 4 hour pre event meal. But the triathlete can take advantage of the 30 to 60 minutes before the event to take a final carbohydrate "boost". As eating while swimming is impossible and inadvertently swallowing water the rule, it makes sense to eat enough complex carbohydrate gel or drink (which will then be slowly emptied into the small intestine over the duration of the swim - with fluids being provided from swallowed water) to replace the Calories that will be expended during the swim (8 to 10 Calories/minute). To minimze GI upset, these carbohydrate Calories should be taken at least 30 to 60 minutes before the swim.

The energy requirements of cycling have been covered elsewhere. As with all cycling events, the key to success is snacking - starting early (during the transition) and continuing to snack regularly during the ride. In the triathlon, where you will be finishing the event with a run, snacking is even more important as any extra Calories taken on board will not only make up for any Caloric deficit from the swim, but will also be available to help you during the run when snacking is much more difficult.

When the run begins, the athlete should be Calorie neutral ie the Calories eaten in the minutes before the swim and during the cycling should equal or slightly exceed the Calories expended during the swim and the ride. Now begins the real challenge - to replace as many of the Calories that will be expended with the run as possible. Running will slow gastric emptying and as a result, snacking may cause nausea. But the new gels and liquid supplements, if taken in small amounts, regularly, can help minimize the phenomena of "hitting the wall" late in the run.

And of course adequate fluid replacement during competition (with particular attention to electrolytes) is essential for these long events.

Remember, along with staying hydrated, Calories are the key, carbohydrates are preferred, and anticipting and replacing your energy needs with regular snacking before you notice hunger will be the most successful strategy.