Carbohydrates: why consume them before training

In this article we will evaluate endurance, endurance exercise, i.e. cycling, running, cross-country skiing and so on. Not only that, what I will take into consideration is, more specifically, the long-term exercise, roughly over 2 hours. What fuel supports it?

Carbohydrates as a fuel

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The answer is: all energetic substances, to some extent: carbohydrates, fats and, at least much less, also proteins / amino acids. The proportion in which the three fuels contribute to muscle work varies from case to case, depending on factors of different types that are beyond our interest today. However, in any case, carbohydrates play a fundamental role, even more so if the exercise is performed at high intensity, even only in some phases: for example a climb or an acceleration. So, as is known, “especially” in those phases, we need carbohydrates to burn. Of these there is a deposit in our body, mainly in the muscles, but also in the liver and is called glycogen. Simply, glycogen is our way of accumulating carbohydrates for their subsequent use. This tank is terribly important, because when it goes “in reserve” we go into crisis, we can no longer carry out our high intensity exercise, we can only “trot” towards the finish line or towards home.

How long does the “fuel” of our body last

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Having said that, a series of questions will arise in you. The main ones will probably be two: 1) how long does the tank last? and 2) how can I make it last longer? Today I will answer the first question and reserve the next articles to answer the second. Now, if an athlete follows a “normal” diet, that is normally rich in carbohydrates, such as pasta, rice, bread, rusks, potatoes and so on, without excesses but not even without restrictions, that is, with good portions of these foods every day, the its glycogen tank has a stably good fuel level. It is not full, certainly, but neither is it scarce. Well, if in a starting condition of this type we start pedaling or running or something else, how long can we continue to do it before the reserve turns on? If the exercise is done without eating or eating very little, an almost constant condition in running, cross-country skiing, swimming in open water, the emptying time will depend on the intensity of the exercise we are doing. Exercise intensity can be measured in various ways, including heart rate. We all know, of course, the higher you go with the intensity, the more your heart rate increases. Of this, each of us has our own maximum, beyond which we cannot go, called the maximum heart rate. We can predict that if we are carrying out our exercise at an intensity constantly around 70% of our maximum heart rate, the glycogen tank will go into reserve after 2 hours on average, while if we are going very fast, at a heart rate of around 90%. of the maximum, the time will obviously be shorter, about 1 hour. In the event that the heart rate is variable between the two values, therefore between 70 and 90% of the maximum, as is likely in many situations, the time will obviously be between 1 and 2 hours. These are very important data for the best nutritional management of demanding performances, which it is useful to know given the general tendency to perform endurance sports in an increasingly prolonged way, i.e. with walking times / distances that a few decades ago were the prerogative of only a few and young competitive athletes, while now they are in the habit or “in the crosshairs” of many more athletes, the majority of amateur level. In the next posts we will develop these issues.