The main fuel for an event like this is carbohydrate, especially if you are completing the race closer to the 4 hour mark than the 7 hour mark. Your body stores contain roughly 500 grams of carbohydrate (this is 2000 kcal), not enough to make it to the finish line. In theory it should be enough to get most athletes through the first 3 hours of a race but topping up from the start is essential. Because it takes time for carbohydrate to be absorbed, you need to start early with fueling to make sure you avoid carbohydrate depletion. Once you run out of carbohydrate stores it is difficult to recover.
As a general rule, aim for 60 grams of carbohydrate per hour (1,2). This carbohydrate can be in the form of a bar, a gel, chews, or a drink. If you use solid foods, make sure fat, protein and fiber content are low (no more than a few grams). What you use is entirely up to you and your personal preferences. Faster athletes tend to use more liquids and less solids because it can be difficult to chew at high intensities.
To give you some idea of what 60 grams per hour equates to, it means that for every hour of the race you would need one of the following combinations:
– 2 gels and a small amount of sports drink;
– 1 gel and a bottle of a sports drink;
– 1 energy bar and half a bottle of a sports drink.
For more accurate calculations check the food labels of the products you are going to use for exact amounts.
“Drinking to thirst” is a recommendation that works fine for the slower athlete. If you are going a bit faster it is better to go in with a plan. It is good to use the early parts of a race when the gastrointestinal tract is working fine to absorb both carbohydrate and fluid. Later in the race, even though you may be thirsty, the gut may not absorb as much. Don’t drink excessively and use common sense. The goal should be to lose a little weight (2 to 4 pounds) at the finish line. You definitely want to avoid weight gain, which clearly would be a s sign of drinking too much. In hot environments dehydration can definitely be a very important factor. Don’t forget that good hydration starts before the race, and hydrate well in the days leading to your race.
A large percentage of athletes, approximately 30 to 70 percent, experience gastrointestinal problems during Long and Middle distance triathlons. Some of these problems are very minor but some of these may be so severe that they will affect performance. Some athletes are more prone to develop these problems than others. The complaints may be totally independent of food intake and sometimes they may only happen on race day. This suggests that “race day anxiety” has something to do with it. Studies have also shown that factors like fibre intake, fat intake and the use of very concentrated carbohydrate drinks are causes of gastrointestinal discomfort. So combining these three main issues, you need to plan ahead and have a rough idea where you are going to get your carbohydrate from (drinks, gels, bars), how much fluid you need to take in and where you are going to get this from (carry, special needs for feed stations) and make sure you reach approximately 60 g/h of carbohydrate intake and enough fluid to not lose a lot of weight. You can get a good idea by weighing yourself before and after training. Think about this in advance and write down your plan.