The importance of sugar and its interactions in the feeling of fatigue
By: Pilar Serrano Galvis. Nutritionist-Dietitian. Technical Department. FunctionalCorp. – Corporation for Functional Nutrition.
For adolescents aged 14 to 19, soccer is among the top 5 sports, in both men and women; however, the level of nutritional knowledge this population group has regarding the relationship between their diet and physical activity is limited and, in most cases, lacking rigor. Given that the rate of malnutrition due to overweight and obesity in secondary school has increased in recent years, teaching lessons on a healthy diet, physical activity, and life skills through sports programs represents an opportunity at this age, and young athletes see in these academic spaces lessons on how to improve sports performance, becoming more than just a routine class (Meng et al., 2018).
Recently, sports have been divided according to the skills required; open-skill sports involve dynamic performance and changing environments, while closed-skill sports are predictable and take place in static environments (Yang et al., 2023). This classification arises from the need to integrate brain functions with the physical and psychological demands of each sport. For example, the hippocampus is the area of the brain where a positive relationship has been demonstrated between aerobic exercise, cognitive function—the strategy—and memory, and it determines locomotion capacity and bursts of speed; the hypothalamus regulates energy metabolism—performance—the cerebellum regulates motor control—movements—and so on, the close energy relationship between different parts of the brain and sports performance has been described, that is, a metabolic conversation between muscles and the brain (Takashi, Soya, & Soya, 2019).
When the brain becomes fatigued…
The brain is perhaps the main consumer of glucose in the body. It has been estimated that a human being with an appropriate weight for their height uses between 130 and 200 g of glucose per day; this is equivalent to 2/3 of the glucose circulating in the blood. Under stressful conditions, for example during an oral exam, glucose consumption can increase by 12%, and during deep sleep, the brain reduces this need by 40% (Peters, 2011). Between 1998 and 2004, the selfish brain theory was proposed as key to understanding neuroenergetic aspects based on the fact that the central nervous system prioritizes the regulation of the glucose availability it needs.
An intermittent high-intensity exercise such as soccer is associated with the consumption of muscle glycogen, reduction of circulating blood glucose levels, increased body temperature, and progressive loss of body water (Meeusen, Watson, & Dvorak, 2006). Scientific evidence from the last 20 years says that the central nervous system has a significant influence on the perception of bodily fatigue; in soccer matches there are periods of intense activity that depend on technique, tactics, and physical, physiological, and mental skills, that is, a fatigued soccer player loses concentration and may make mistakes in any or all of the skills required for their work.
Glycogen is a very important source of energy for the brain; it is the “sugar” form in animals, useful for many organs and tissues, and when muscle and liver reserves are depleted, hypoglycemia occurs (Matsui et al., 2011), even before the reserves available to neurons in nervous system tissues are depleted. But prolonged exercise also depletes brain glycogen levels and induces changes associated with the feeling of fatigue in a high-performance athlete. The benefits of supplementing a player with simple carbohydrates such as sugar, before, during, and after long and intense exercise, also contribute to maintaining stable glycemia levels for the brain, preserving functional and cognitive performance, reducing central fatigue, and prolonging endurance time, which is very important in a match of at least 90 minutes (Meeusen, Watson, & Dvorak, 2006) (Yang et al., 2023).
Cognitive performance is the mental action or process of acquiring knowledge and understanding through experience and feeling. Applied to sport, cognitive functions are frequently measured and include executive functions—the ability to execute—the ability to process spatial information, attention, and memory (Yang et al., 2023).
In practice, the executive function of a soccer player consists of placing thought before action, mastering the challenges that arise, and maintaining concentration during periods of sensory overload, which is known as “central fatigue” and depends on the amount of glycogen available to the brain. It is widely known that sports drinks (based on sugars and replacement electrolytes) help improve performance and endurance, promoting not only hydration but also the energy from added sugars as an additional substrate to muscle glycogen; there are many studies aimed at understanding the regulation of energy supply, but we can fall into simplicity by assuming that ingesting sugars will improve executive performance. This should be the result of a sports evaluation of individual performance.
Hydration
The main constituent of living organisms, an essential requirement for life, is water. It has numerous physiological functions, creating an appropriate medium for biochemical reactions within and between cells, and for the different cellular and metabolic responses to stress. Its components, Hydrogen and Oxygen, exceed the amount of glucose, calcium, magnesium, and potassium, and it improves the functions of the cellular refinery, the mitochondrion, which generates all the energy necessary for biological processes, especially in the tissues that need it most, such as muscles and nerves, where insulin is also essential (Kharaeva et al., 2021).
We can say, then, that as the practice of soccer is encouraged as a strategy to increase the level of physical activity among school-age students, a few hours can be dedicated to learning more about nutrition focused on sport and the importance of sugar as a nutrient that ensures not only sports performance, but also the cognitive capacity to compete, avoiding the feeling of fatigue and maintaining a balanced metabolic state for longer.
The Bonus
In older adults, the effect of physical activity on cognitive functions is well documented; it can delay their decline and brain aging. Functions such as memory, attention, and rapid processing, which are known as executive functions and are high-order cognitive processes for monitoring and managing multiple basic functions and problem-solving behavior. For example, adaptation to changes in scenario, updating, inhibition, attention control, planning, and verbal fluency (Dai, Chang, Huang, & Hung, 2013).
Bibliography
Meeusen, R., Watson, P., & Dvorak, J. (2006). The brain and fatigue: New opportunities for nutritional interventions? Journal of Sports Sciences.
Matsui, T., Soya, S., Okamoto , M., Ichitani, Y., Kawanaka, K., & Soya, H. (2011). Brain glycogen decreases during prolonged exercise. J Physiol , 3383 – 3393.
Yang, J., Han, Q., Liu, Q., Li, T., Shao, Y., Sui, X., & Wang, Q. (2023). Effects of carbohydrate drinks ingestion on executive function in athletes: a systematic review and meta-analysis. Front Psychol. Front Psychol.
Dai , C.-T., Chang , Y.-K., Huang, C.-J., & Hung, T. M. (2013). Exercise mode and executive function in older adults: An ERP study of task-switching. Brain and Cognition.
Meng , Y., Manore , M. M., Schuna , J. M., Patton-Lopez, M. M., Branscum, A., & Wong, S. S. (2018). Promoting Healthy Diet, Physical Activity, and Life-Skills in High School Athletes: Results from the WAVE Ripples for Change Childhood Obesity Prevention Two-Year Intervention. Nutrients.
Takashi, M., Soya, M., & Soya , H. (2019). Endurance and Brain Glycogen: A Clue Toward Understanding Central Fatigue. Brain Glycogen Metabolism.
Peters, A. (2011). The selfish brain: Competition for energy resources. . Am J Human Biol.
Kharaeva, Z., Hokonova, T., Elmurzaeva, J., Dzamihova, I., Mayer, W., De Luca , C., . . . Korkina , L. (2021). Effects of Heavy Isotopes (2H1 and 18O16) Depleted Water Con-Sumption on Physical Recovery and Metabolic and Immunological Parameters of Healthy Volunteers under Regular Fitness Load. Sports (Basel).
Yang, J., Han, Q., Liu, Q., Li , T., Shao , Y., Sui, X., & Wang, Q. (2023). Effects of carbohydrate drinks ingestion on executive function in athletes: a systematic review and meta-analysis. Front. Psychol.
Yang , J., Han , Q., Liu , Q., Li , T., Shao, Y., Sui, X., & Wang, Q. (2023). Effects of carbohydrate drinks ingestion on executive function in athletes: a systematic review and meta-analysis. Front Psychol.
