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The focus on glycogen overload

Our body needs a good supply of energy when running long distances. To that end, we have been studying glycogen overload since the 1960s. Since then, methods have evolved to experience fewer side effects. Let’s take stock of the right method to practice to fill up your energy reserves before a race.

What is glycogen?

Glycogen is the store of carbohydrates stored in the muscles and liver. This reserve is approximately 500 g, of which about 100 g in the liver and 400 g in the muscles, or more precisely 15 g of glycogen per kg of muscle. Glycogen is produced from carbohydrates that are consumed in fruits, starchy foods and sugars.

Is it necessary to fill up glycogen reserves before exercise?

Our reserves of glycogen allow us to carry out a sports activity, without needing to eat before or during. However, since glycogen stores are depleted during exercise, especially during high intensity (> 60% VO2max) and long duration (> 90 minutes) efforts, it is best to fill up your reserves before a race. more than 21 km. Reserves full of energy will help to delay fatigue and maintain good running speed.

What is the best way to fill your glycogen stores?

Previously, it was suggested to deplete glycogen stores with a very demanding training followed by a drastic reduction in carbohydrate intake for 3 days. Then, we reintroduced a very high intake of carbohydrates during the 3 days preceding the race, which allowed to overcompensate, that is to say to store more glycogen than the body does normally. However, this method involves undesirable effects that may put at risk the performance of a runner. Indeed, training as demanding a few days before an event puts the runner at risk of injury. In addition, the variation in carbohydrate intake can lead to significant gastric problems.

Now, it is known that the depletion of glycogen stores with intense effort is no longer necessary. Simply increase carbohydrate intake as training decreases, and only 2 days are enough for experienced athletes. It should be known that even if the first method allows to fill more its reserves of glycogen, this extra will be used more quickly by the body and the glycogen concentrations will be comparable for both methods after about one hour of effort.

What should I eat to fill my glycogen stores?

In the 36 to 48 hours before the race, you need to gradually eat more carbohydrates, as the training decreases. You should aim at about 10 g of carbohydrate per kilogram of body weight and consume more fluids than usual. In addition, as energy expenditure falls, it is necessary to balance the caloric intake by reducing the fat intake. It is also preferable to follow a diet low in fiber, to reduce the contents of the intestine for the day of the race and limit bloating. Thus, a 70 kg man will need about 700 g of carbohydrates via refined grains, unpeeled fruit, juice and added sugars. He will also have to avoid alcohol and not limit his salt intake.

It is important to note that the simple application of the glycogen overload protocol is not a guarantee of success. Feeding the very morning of the race is just as important. You need to eat enough carbohydrate in the hours before exercise to fill the liver with glycogen stores. One should consume about 1g of carbohydrate per kilogram of body weight per hour before the test, for example the equivalent of 140g of carbohydrates for a 70kg man who would do his marathon in 2 hours.

For example, here is what the menu of a day before a long race might look like (by repeating a similar day for the 2nd day of overload required):

  • Lunch: French toast with white bread, maple syrup, and orange juice
  • Snack: canned pineapple and mozzarella cheese
  • Dinner: Salmon bread and beetroot soup
  • Snack: Greek yogurt with vanilla and applesauce
  • Dinner: Tonkinese soup (salted broth, chicken and rice noodles)
  • Snack: Cereals of puffed rice, almond milk and banana



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