Glycogen stores

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The glycogen store (also glycogen depot ) in the human body refers to the carbohydrates stored in the cells of various organs in the form of glycogen . Depending on the muscle mass, one third of the stored glycogen is in the liver (up to 150 grams of glycogen, i.e. around 10% of the mass of the liver) and two thirds in the muscles (up to one percent of its own weight). The liver glycogen is used to maintain the blood sugar level and thus to supply the brain , red blood cells and nerve cells with glucose. The glycogen stores in the muscle fibers cannot contribute to blood sugar regulation, but through the formation of glucose-6-phosphate and glycolysis enable the resynthesis of the “cell fuel” ATP , which is required for muscle contraction (cf. energy supply ).

As a polysaccharide , like starch , glycogen is highly hygroscopic and is therefore stored in the cells with the help of water. The often rapid weight loss in the first few days of low-carb diets can be explained by the loss of this water. Consequently, carbo-loading diets (see below) also lead to an extremely rapid increase in weight of up to 2-3 kg due to the storage of water.

The importance of glycogen stores in sport

The energy carrier ATP, which is ultimately necessary for muscle work, can be obtained in two ways: on the one hand by glycolysis, i.e. the breakdown of carbohydrates from glycogen stores, and on the other hand by beta-oxidation , the breakdown of free fatty acids (which swim in the blood) and the subsequent citric acid cycle and the Respiratory chain . The aerobic glycolysis supplies about two and a half times as much ATP as the beta oxidation and thus enables a higher exercise intensity.

While the body's fat deposits are sufficient for several weeks to supply energy even for thin people, the glycogen store can provide energy for around a day under normal stress. On the other hand, with intense exercise, the glycogen stores are exhausted after about 90 minutes.

It follows that a particularly long and a particularly intensive load are mutually exclusive. Endurance athletes have to conserve their glycogen reserves by not choosing their intensity (e.g. running pace) too high. In addition, they can use their specific training through basic endurance improve, to increase the power converted by beta oxidation amount of energy. To a certain extent, it is also possible to ingest and process carbohydrates during exercise. In order to conserve or stretch the glycogen stores, this is done right from the start (examples: long-distance swimming , marathons , road cycling , triathlons ).

A normal, untrained person has a glycogen store of around 300 to 400 g of glycogen. Well trained endurance athletes can have a much larger glycogen store of up to 600 g.

Maximize glycogen supplies before competitions

Schematic representation of the desired effect of the three variants of the carbohydrate diet before a competition.
X-axis: time, period here about a week;
Green Line: Simple Carbohydrate Diet;
Yellow line: Carbohydrate diet with previous emptying of the glycogen stores;
Red line: Saltin diet

In order to have as large a supply of glycogen as possible during a competition , athletes use various diets in the run-up to the competition, which are known as "saltin diet", "carbohydrate fattening" or "carbo-loading". The three different forms of these diets have in common that they attempt to build up a large amount of glycogen through excessive carbohydrate intake in the days leading up to the competition. The effectiveness and medical advisability, especially of the extreme form of the saltin diet, is, however, controversial.

Simple carbohydrate diet

Carbohydrate-rich food on the days before the competition should replenish the glycogen stores.

Carbohydrate diet with prior emptying of the glycogen stores

Before a large amount of carbohydrates is consumed, as in the simple KH diet, the glycogen stores are emptied by a final, intensive training session and then filled again immediately afterwards. In the sense of supercompensation , an even better filling of the glycogen reservoir should be achieved.

Saltin diet

The saltin diet is the extreme form of carbo-loading . It is carried out in three steps:

  1. The glycogen deposits (especially in the muscles) are emptied through endurance training with a simultaneous decrease in KH supply.
  2. In the following “fat-protein days”, attention is paid to a low-carbohydrate diet, which means that the glycogen stores are barely filled. In the meantime, endurance training continues.
  3. A final endurance run empties the glycogen stores further. In the last two to three days, the carbohydrate content in the food is increased drastically in order to replenish the depots to the maximum.

The principle of the saltin diet is the “super compensation” of KH. By extremely reducing the carb intake in the first two steps of the diet, the body tries to compensate for the lack of glycogen in the end phase. However, a sudden increase in the glycogen intake leads to supercompensation, which means that the body now stores carbohydrates beyond the normal level. The athlete has KH available for energy production over a longer period of time. The saltin diet, however, leads to a strong weakening, since the glycogen stores are completely emptied in the first two days. This increases the risk of infections above average. The “competitive morale” can also suffer greatly from the weakening. In addition, the supercompensation model is considered to be secure for the glycogen stores of beginners, but for those of highly endurance-trained athletes, a significant additional effect is questioned, as they regularly reduce their glycogen stores significantly in basic training.

See also

Individual evidence

  1. Wastl, energy supply ( memento of the original from February 28, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF file; 71 kB) , p. 7.  @1@ 2Template: Webachiv / IABot / user.phil-fak.uni-duesseldorf.de
  2. ^ According to Herbert Steffny : The large running book . Südwest, Munich 2011, ISBN 978-3-517-08642-2 .

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