How do you use nutrients during an Ironman?

Triathlon is a sport that put together three different sport modalities: swimming, cycling and running, in that specific order. Although nowadays there are many different distances for this sport, the most challenging one is the Ironman.

In Ironman the athletes are supposed to swim along 2.4 miles (or 3860 meters), ride along 112 miles (or 180 km) and run a full marathon (26.2 miles or 42km). The average time to complete this competition is about 12 hours and 36 minutes, although high performance athletes can do it in less than 9 hours. In any case, an Ironman is considered a long-distance competition that comes with some nutritional challenges.

A long-distance exercise is considered an endurance exercise, or an exercise that cannot be sustain as high intensity as a short distance exercise, mainly because energy sources. The moment in the exercise that any person spends more energy are the first approximately 12 seconds of exercise, mainly because the body must be taken from its inertia state and it requires a large and fast source of energy that comes from a system called
ATP-CP. As the name suggests the ATP-PC system consists of adenosine triphosphate (ATP) and phosphocreatine (PC). This energy system provides immediate energy through the breakdown of these stored high energy phosphates. However, after the body runs out of this energy very fast and depends of a second energy source to keep the intensity of exercise: Glycolysis.

Glycolysis is the catabolism (break down) of carbohydrates, as glucose and glycogen, by enzymes, with the release of energy. That can either happen in an aerobic or anaerobic way (with or without oxygen). Although this process occurs along all time of exercise, it is more intense in the beginning of exercise. Depending on how adapted an athlete is or not to the exercise it can be the main source of energy to the exercise for 2 to 30 minutes. However, the average Ironman athlete does use this energy system as main form of energy along about 5 minutes.

That is the moment of exercise where the main source of energy comes from lipolysis, or the breakdown of fat strict dependent on the consumption of oxygen (aerobic). At this point, the aerobic glycolysis is still maintaining, but is no longer consider the main source of energy to the body.

The main problem found along these metabolic changes is that the body sources of carbohydrates (either as glucose and glycogen) are very limited, and even a carbo-loading before a competition will not give much more than 500 grams of carbohydrate (as glycogen) to the body, what will be enough for only two hours of an endurance exercise. That will force the body to adapt decreasing sport performance and/or depleting muscle to convert its protein in to carbohydrates sources.

The only way to avoid or minimize these adaptations is the consumption of carbohydrates along exercise. the sooner and the bigger is the replacement of carbohydrates the smaller will be depletion of protein and loss of performance.

However, the supplementation of carbohydrates has some limitations that includes: time of digestibility, absorption and dependence of water. That makes almost impossible from an average man (155 lbs or 70kg) to consume all his needs of carbohydrate, specially because it should star with no more than 30 minutes of exercise to be the lowest damage as possible to the body, time where an Ironman athlete is still in the water.

Those complicated factors make us understand why all long-distance exercise sessions (3 hours or more) are very damage to the human body and depend on a perfect recover after the exercise to do not cause definitely damages the body. The sooner the glycogen levels are restored after a long training session, it will diminish the damage cause to the body; making the athlete recover faster for his next exercise session.

Perlow-Friedler, G

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