Glycogen and its effects on runner performance

Image by Daniel Reche from Pixabay

Carbohydrates or saccharides are a group of organic molecules that are divided into monosaccharides (one unit), disaccharides (two units), and polysaccharides (several units) depending on the number of molecules of simple carbohydrates.

Monosaccharides and disaccharides are also known as sugars. Glucose (blood sugar) is the most important monosaccharide that provides energy for muscle contraction (work).

Glucose molecules joined together to form a specific polysaccharide called glycogen. It is stored in our muscles and liver and breaks down into individual glucose molecules in muscle cells when necessary for energy production.

The importance of glycogen
Based on the results of scientific research, some conclusions were made why glycogen is so important when performing endurance exercises:

  • Muscle glycogen reserves are systematically consumed at loads of 77 percent of VO2max;
  • The amount of glycogen in the muscles at the time of depletion approaches zero;
  • Duration to failure is directly related to the amount of glycogen in the muscles.

The muscles of a healthy man who regularly consumes a sufficient amount of carbohydrate food can contain about 600 g (2400 calories) of carbohydrates in the form of glycogen, and another 90 g in his liver.

A high-carb diet is a key to preserving and increasing glycogen stores. The easiest way to maintain its required amount is to use foods high in carbohydrates (or sports nutrition) during heavy training or competition.

During the competition, immediately after the start, your glycogen stores begin to gradually become depleted, especially during the first hour, as well as with increasing intensity. In the later stages of the race, blood glucose and free fatty acids will be used as energy.
Replenishment of glycogen reserves is one of the most important tasks at the end of a competition or in the long run. Research has found that chronic carbohydrate depletion reduces performance during heavy training. The highest glycogen recovery rate is observed immediately after completion of the load when eating foods high in carbohydrates.

Glycogen levels return to normal within 24 hours if you eat carbohydrate-rich foods immediately after training and throughout the day.

A study published by Benjamin Rapoport in Harvard Gazette in 2010 shows that the likelihood of a wall effect during a marathon depends on the amount of glycogen in the muscles, pace, body size, and muscle mass.

These variables are closely related to each other. For example, running at a higher pace burns more glycogen than fat, and this allows you to overcome the distance faster, but most people do not have such reserves. In addition, there is a factor that Rapoport did not take into account: later studies have revealed that the brain, in order to avoid complete depletion of glycogen, gives the body a command in advance to reduce its speed.

A follow-up study published in the Journal of Applied Physiology in 2011 examined the effects of training at high and low glycogen stores. For this, 20 cyclists were selected, who were divided into 2 groups, and used the same diet and training plans. The first one spent all its workouts in the morning on an empty stomach, while the second took a carbohydrate-rich breakfast 90 minutes before their daily workout, which consisted of 60-90 minutes of high-speed cycling in the morning.

After six weeks of training, both groups showed the same improvement during the 60-minute race. Nevertheless, certain changes occurred in the “hungry” group, which indicated that their bodies more efficiently used fat as fuel. The number of enzymes responsible for the processing of fats was significantly higher than in the second group, in addition, the use of fat as a fuel increased with increasing intensity. This allows us to conclude that participants in the first group can maintain a given pace with lower glycogen stores, which reduces their chances of achieving the “wall” effect.

If you want to avoid this extremely unpleasant state while running long and extra-long distances, consider including running sessions on an empty stomach in your training process.


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