Glycogen Deficiency: The Hunger Crisis in Sports

A hunger crisis in sports refers to a situation where an athlete's glycogen reserves, particularly in the muscles, are insufficient to sustain the physical effort required. This can lead to a sharp drop in performance, accompanied by symptoms like intense hunger, a sense of weakness, and a general feeling of discomfort, as the athlete feels "drained" of energy.

This phenomenon is typically seen in endurance athletes, such as marathon runners and cyclists, who require sustained energy over long periods. It is less common in sports that involve shorter, more intense bursts of effort. Amateur athletes and novices are also more likely to experience hunger crises, either due to their inexperience in managing their diet or their metabolic inefficiency in conserving glycogen by oxidizing high percentages of fatty acids even at medium to high intensity levels.

The Role of Glycogen

To fully comprehend the onset of hunger crises in sports, it's crucial to understand the significance of glycogen reserves in physical activity. As energy consumption increases during sports, the body relies on the hydrolysis-oxidation of energy molecules, including carbohydrates, fatty acids, branched-chain amino acids, and substrates for neoglucogenesis.

While these energy metabolisms are not separate and usually occur simultaneously, the level of training, metabolic efficiency, type of effort, duration of effort, nutritional state, and individual differences can affect the energy expenditure and prevalence of metabolic pathways. Nevertheless, carbohydrates (glucose) always play a part in the energy production mechanism, whether in aerobic, anaerobic, or mixed efforts.

Glycogen Reserves

Glycogen, a complex carbohydrate and a polymer of glucose, along with glucose already dissolved in the blood, represents the only available source of carbohydrates for the body. On average, the adult organism can contain approximately 300-400g of glycogen, located mainly in the liver (25-30%) and muscles (70-75%), with a minimal amount in the kidneys (approximately 1-2%).

The purpose of glycogen varies depending on its storage location. Hepatic glycogen is necessary for maintaining blood sugar levels, muscular glycogen supports the contractile effort, and renal glycogen maintains filtration efficiency. However, glycogen reserves have a limited capacity and can only be increased to a certain extent with training.

Preventing Hunger Crises

Preventing a hunger crisis during sports requires the athlete to consume a diet rich in complex carbohydrates and allow their body to recover from the physical stress induced by training. A suitable diet would provide a quantity of carbohydrates ranging between 55 and 60% of the total calories, proteins should not exceed 1.5 g/kg of body weight, and fats should be between 25 and 30% of total energy.

What sets the diet of an endurance athlete apart from a sedentary person is the energy distribution in the various meals of the day. Athletes perform demanding physical activities that significantly contribute to increased caloric needs. Therefore, the energy provided by carbohydrates should be distributed throughout the day, with a higher density before, during, and immediately after physical activity.

In conclusion, to prevent a hunger crisis from occurring during sports due to the depletion of muscle glycogen, it is necessary to introduce the right amount of energy and carbohydrates, properly distribute the nutrients and daily meals, allow the body to recover properly, and manage energy during the performance to avoid running out of glycogen reserves prematurely.

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