- Glycogen - feature
- When is glycogen converted into energy?
- Glycogen - occurrence. Where is glycogen stored?
- Muscle glycogen levels and physical performance
- How to effectively replenish glycogen levels after training?
- How to build up glycogen stores before training?
- Pre-training meal - recommendations:
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Glycogen is a polysaccharide that fuels working muscles. The more glycogen we have, the more our muscles can work longer and more efficiently. How to accumulate glycogen reserves before exercise and how to replenish its deficiency after training? See what and when to eat to have energy for long, intense exercise.
Glycogenis an animal starch-like storage polysaccharide (polysaccharide) that consists of many glucose molecules linked together. It is stored mainly in the muscles and the liver. It is made of carbohydrates supplied to the body from the diet. It is the main fuel for working muscles.
Glycogenis made by a process called glycogenesis. It occurs in the liver and works by binding blood glucose to form glycogen. Glycogenesis is activated in the liver during rest periods and is initiated by insulin produced by the pancreas in response to high blood glucose levels (e.g. by eating a high carbohydrate meal).
Glycogen - feature
Food and drinks contain four main ingredients that can be used to generate energy:
- carbohydrates,
- proteins,
- fats,
- alcohol.
When you eat a meal or drink fluids, these compounds break down in the digestive system into essential elements which then pass into the bloodstream. All these compounds are meant to produce energy. Carbohydrates, including glycogen, break down into small molecules of simple sugars: glucose, fructose and galactose. Mainly used for short-term energy production, while fats are an energy reserve for a longer period of time. Proteins can be converted into energy in "emergencies", such as when carbohydrate resources are depleted. Sooner or later, all food components break down, releasing energy.
When is glycogen converted into energy?
During exercise, the body uses three energy systems that it can use for different types of physical activity:
- ATP-PC pathway (phosphagen system),
- anaerobic glycolysis (lactate glycolysis),
- oxygen glycolysis - it is during this process that the body draws energy from the accumulated onesglycogen stores.
The ATP-PC pathway dominates during maximum physical efforts of up to 6 seconds. It is used, for example, when pulling a barbell or during a long or high jump.
Anaerobic glycolysis turns on when you start exercising very intensively. It dominates during physical exertion of up to 90 seconds, such as a quick run of 400-800 meters or strength training.
When you start exercising, you initially use the ATP-PC pathway and the anaerobic glycolytic pathway, but after a few minutes your energy reserves "switch over" to the oxygen system.Most of the carbohydrate broken down in aerobic glycolysis comes from muscle glycogen . Muscle glycogen cannot supply energy indefinitely because the body stores it in a relatively small amount. As you continue to exercise, after training for more than an hour, your muscle glycogen stores become depleted and your blood glucose conversion increases to energy.
During the period of frequent and intense training, make sure that the dietary components, which are the source of energy, are quickly digested, absorbed and burned by the body, and their surpluses are effectively stored in the form of readily available stocks. Among all the energy components provided in the diet, only carbohydrates meet the above conditions, therefore their participation in the diet of athletes and physically active people is particularly important.
Glycogen - occurrence. Where is glycogen stored?
The human body has the ability to store sugars, mainly in the form of glycogen. Their reserves are distributed in the body as follows: approximately 79% in muscle (muscle glycogen), 14% in liver (liver glycogen) and 7% in blood (glucose).
The content of hepatic glycogen is variable and ranges between 60-150 g. The lowest values of hepatic glycogen are observed on an empty stomach or after a period of starvation, while after eating a meal containing carbohydrates, its resources in the liver are increased.
10% of the glucose in food is used for the synthesis of muscle glycogen. In the event of insufficient food supply, hepatic glycogen is the basic source of glucose stores for the nervous system and red blood cells. Muscle glycogen content, similar to that of the liver, is variable. In an athlete's body, with proper training and nutrition, his total reserves can increase to about 500 - 600 g, of which 70 g is liver glycogen and the rest is muscle glycogen.
Muscle glycogen is only a sourceenergy for muscle cells.During long and intense workouts, the size of its resources is of great importance. During training, the reserves of carbohydrates accumulated in the muscles are reduced, which in turn leads to a significant decrease in the intensity of exercise. When glycogen reserves are significantly depleted, problems with coordination may arise. The work of the brain is disturbed, for which glucose is the main source of energy. These resources are 1600 - 2000 kcal (in the case of an average organism) and are enough to survive one day of total starvation. For this reason, people starting a low-carbohydrate diet lose a lot of weight in the first few days. This rapid weight loss is caused almost entirely by the loss of glycogen and water. On the other hand, people practicing endurance sports have a higher concentration of glycogen in their muscles compared to people who lead a sedentary lifestyle.
Muscle glycogen levels and physical performance
An athlete's physical performance depends on the size and energy resources accumulated in the body. Too low energy supply causes too quick depletion of the body's energy reserves and premature termination of exercise, catabolism of muscle proteins or will increase the risk of injury.
The most important source of energy in high-intensity training (>80% VO2max) is carbohydrate stored in the muscles and liver in the form of glycogen. Their number is enough for about 60-90 minutes of intense effort. In the case of medium or moderate intensity exercise (60 - 80% VO2max), their amount is sufficient for approx. 2-3 hours. However, if the right amount and quality of carbohydrates is not respected in the diet, exhaustion occurs much faster. In the case of athletes in periods with high energy demand (e.g. before competitions), there is a need to include supplementation to compensate for energy and nutrient losses. The more intense the training you perform, the more you will reduce the level of stored glycogen. During very intense exercise (>90% VO2max), the consumption of glycogen in fast twitch fibers is much higher than in slow twitch fibers, therefore sprinters have a greater need for carbohydrates than people practicing endurance sports. Sprinters have a problem with muscle glycogen regeneration, which is slower compared to typical endurance sports such as running or cycling, and this is a result of greater muscle damage. Both for amateurs before training in the gym, and for athletes beforeIn competition, your muscle carbohydrate stores (muscle glycogen) determine when fatigue occurs. People practicing sports should use an appropriate nutritional strategy depending on the type of physical activity, taking into account a sufficiently large amount of carbohydrates that will provide fuel for an intense workout. The rate of glycogen restoration after exhausting exercise is about 5% per hour, as a result of which full resynthesis of this component is possible only after 20 hours. In the case of a low-carbohydrate diet, this process may be significantly extended. In the process of rebuilding glycogen, not only the right amount of carbohydrates is important, but also the speed of their administration after exercise. After hard training, glucose penetrates into the muscle cells very quickly. Under normal conditions, out of 100 g of glucose ingested, only 20 g is absorbed by the muscles. After very hard training, your muscles can capture up to 60 g of glucose! Consequently,it is very important to get carbohydrates preferably immediately after training or up to 30 minutes after completing . The optimal amount is 50 g, which allows for a 10% faster rate of glycogen re-synthesis. Research studies (Blom, 1987) showed that the consumption of 25 g of carbohydrate in the form of glucose at 2-hour intervals after exercise resulted in only 2% of glycogen restoration. Glycogen synthesis is most intense within 5-6 hours after exercise, so during this time it is advisable to consume 200 g of carbohydrates with a high glycemic index contained in various foods and fluids. After 5-6 hours, when the glycogenesis process is slower, it is recommended to eat products with a lower glycemic index (e.g. coarse grain products, groats, dark rice, vegetables). In the period of up to 5 hours after training, fat consumption should be limited, especially of animal origin, because the saturated fatty acids contained in them inhibit the transport of glucose through cell membranes and reduce the sensitivity of insulin receptors. In addition, foods containing large amounts of fat are digested for a long time and suppress the appetite for many hours, which may translate into insufficient supply of lost carbohydrates. Carbohydrate loading (carboloading) 1-2 days before training Carboloading, or carbohydrate loading, is a modification of the diet and training loads, resulting in the accumulation of glycogen. Veryintense effort, both running 40 km in a marathon, taking part in a bicycle competition when we have to pedal for 60 km, or even a football match lasting 90 minutes, requires a lot of energy. How to fully charge your tank so that we have enough strength for very intense, sometimes even extreme efforts? Current research suggests that for most sports, especially team sports,24-36 hours of a high-carbohydrate diet(depending on the discipline from 8 to 10 g per kg of body weight ) before the start, while reducing the intensity of training, without an initial, violent phase of depletion of its resources in the muscles. The main source of carbohydrates at this time should be products such as: rice, porridge, pasta, bread, potatoes, sweet potatoes, fruit and fruit juices. However, before you introduce this method before taking off, check first how it works for you during training. How to recharge glycogen just before training? The pre-training meal allows you to replenish the circulating energy in the blood just before exercise, but this amount does not exceed 5 g of glucose (in the blood). Thanks to this meal, we will reduce the feeling of hunger and maintain an optimal level of energy. However, in the case of athletes competing in competitions, the consumption of a meal in the period immediately preceding exercise is not as important as the adequate amount of carbohydrates provided systematically, 1-2 days before exercise. Sample carbohydrate meal before training (to be eaten 3-4 hours before exercise): Examples of carbohydrate snacks before training (to be eaten 1-2 hours before exercise):How to effectively replenish glycogen levels after training?
How to build up glycogen stores before training?
Pre-training meal - recommendations:
About the authorAgata Dąbrowska, personal trainer, fitness instructor, dietitian Certified personal trainerinternational class, fitness instructor, dietitian and a graduate of Chemistry at the University of Warsaw. She has been involved in sport for 4 years. A great enthusiast of fitness and he althy eating. A real volcano of energy that can motivate almost everyone to fight for better he alth and a beautiful figure. Privately, she loves to cook. In her kitchen, every dish can be made fit. Its motto is: "To be successful, the first thing you have to do is fall in love with the hard work."
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