During races lasting 60 minutes or longer, the primary concerns of the athlete are hydration, energy, and electrolytes. In this situation, we want to use the most readily available and easily digestible energy sources, which are the simple sugars glucose and fructose. Athletes want to avoid protein, fiber, and fat as they slow digestion and can lead to GI issues during the race.
Note that some BCAAs have shown benefits in limited clinical trials as well as some advantages to protein supplementation for ultra-endurance events at very low intensities. If competing in races longer than IRONMAN, this is something to consider.
The goal is to consume the following:
Consume 60 to 90 grams of carbohydrates with a mix of 2:1 glucose (dextrose, maltodextrin) to fructose per an hour.
Some athletes may have an intolerance to fructose (~40% of North Americans) and should aim for 60 grams an hour of glucose while others may have to work on reaching the high end of the spectrum with 90 grams of carbohydrates an hour.
The best way to deliver carbohydrates is in simple forms (dextrose, maltodextrin, fructose) as a fluid. For races where hydration is the primary goal (short/hot courses) aim for 4% and for long races where energy replenishment is the target aim closer to 12%. At the IRONMAN and IRONMAN 70.3 distance, a solution of 8% (isotonic) is ideal. Most sports drinks such as Gatorade Endurance are between 6 and 8%.
Supplement with solids such as Gu Energy Chews if required. The key is to take solids in slowly over time while chasing them with fluids to maintain the ideal solution ratios.
A benefit is to push the carbohydrate at a higher ratio of 8-10% on the bike to allow for a “fuller” state heading into the run. On the run, athletes may find 4-6% easily tolerable while having to work to achieve 7-8%.
When racing IRONMAN distance or longer all athletes will slow during the back end of the marathon as glucose requirements outpace the physiological implications on consumption. As a result, athletes will begin to rely more and more on fat stores.
Use a sweat rate test to determine fluid needs during racing or aim for roughly one liter per an hour. The maximum absorption rate for most athletes is 32 to 40 oz per an hour. A simple goal is to focus on peeing once during an IRONMAN 70.3 and twice during an IRONMAN.
Aim for 500 – 700mg of sodium per 32 oz of fluid. For heavy sweaters (those with salt stains post workout), aim for 700 to 1000mg of sodium per 32 oz of fluid. Ensure that you consider sodium across all energy sources and supplement to these amounts as needed. Human kidneys are amazing at conserving and excreting additional electrolytes through urine. As a result, the primary path for loss electrolytes is through sweat. Thus athletes can under-consume what is sweated out, but will rarely over consume what the kidneys can excrete.
Make sure to practice these nutrition goals in your race specificity workouts and your long weekend workouts. For shorter duration workouts or non-race, specificity/practice workouts continue to use your exercise guidance such as P+C Drinks.
For more clarification, work with your assigned coach.