Central fatigue is one of the main limiting factors in endurance sports performance. Unlike peripheral fatigue, which occurs directly in the muscle, this type of fatigue involves the central nervous system and is related to changes in neurotransmitters, perceived exertion, and motivation throughout exercise.
In this context, nutritional strategies play a fundamental role in modulating these mechanisms, helping to preserve brain function and sustain performance.
What is central fatigue and how it impacts performance
Central fatigue is associated with changes in brain activity during prolonged exercise, especially in the balance between neurotransmitters such as serotonin and dopamine.
During long efforts, there is an increase in serotonin production, which is associated with feelings of sleepiness, reduced motivation, and increased perceived exertion. At the same time, a relative decrease in dopamine may impair focus and the ability to maintain intensity.
This imbalance directly contributes to performance decline, even when the muscles are still capable of continuing the exercise.
Carbohydrates and the central effect, much more than energy
Carbohydrate intake during exercise does not act only as an energy source. It also has a direct effect on the central nervous system.
The presence of carbohydrates in the oral cavity is already capable of activating brain areas associated with reward and motor control, reducing perceived exertion and improving performance, even without actual ingestion, a phenomenon known as carbohydrate mouth rinse.
In addition, adequate carbohydrate availability reduces the release of free tryptophan in the blood, which may attenuate the increase of serotonin in the brain.
Practical application:
Maintain regular carbohydrate intake during exercise, between 30 and 90 g per hour, depending on duration and intensity
Use multiple carbohydrate sources, such as glucose and fructose, to optimize absorption
Consider strategies such as carbohydrate mouth rinse at specific high intensity moments
Caffeine as a modulator of the central nervous system
Caffeine is one of the most well established strategies to reduce central fatigue. Its main mechanism involves blocking adenosine receptors in the brain, increasing alertness and reducing perceived exertion.
In addition, caffeine may contribute to greater motor unit recruitment and improved focus during critical moments of a race.
Practical application:
Recommended dose between 3 and 6 mg per kg
Can be used before and or during exercise
A split strategy throughout the event may help sustain its effects
Amino acids and the tryptophan hypothesis
Branched chain amino acids, especially BCAA, have been proposed as a strategy to reduce tryptophan entry into the brain by competing for the same transporter.
Although the theory is interesting, current evidence is inconsistent regarding its direct impact on performance. Still, in specific contexts, there may be indirect benefits, especially when combined with other nutritional strategies.
Hydration and electrolytes, impact on brain function
Dehydration, even at mild levels, is enough to increase perceived exertion and impair cognitive functions such as attention and decision making.
Sodium, in turn, is essential for maintaining plasma volume and neuromuscular function, directly influencing communication between the brain and muscles.
Practical application:
Avoid losses greater than 2 percent of body weight
Adjust fluid intake according to sweat rate
Ensure adequate sodium replacement during exercise
Integrated strategies for endurance events
Central fatigue does not depend on a single factor, but rather on the interaction between energy availability, hydration status, and neurochemical modulation.
Therefore, the best approach involves combining strategies:
Adequate carbohydrate intake throughout the event
Strategic use of caffeine
Maintenance of hydration and electrolyte balance
Training of the gastrointestinal tract for nutritional tolerance
Central fatigue is a key determinant of endurance performance and is directly linked to central nervous system function.
Well planned nutritional strategies, especially involving carbohydrates, caffeine, and hydration, are effective tools to modulate these mechanisms, reduce perceived exertion, and sustain performance throughout exercise.
Reference
Zhang, Y. et al. Exercise induced central fatigue, biomarkers and interventions. Frontiers in Physiology, 2024. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC12096901/
