Caffeine is one of the most widely used resources in sports nutrition and also one of the most debated. While many athletes report clear improvements in performance, others still question whether its effects are truly physiological or merely perceptual.
To answer this, we need to understand how it acts in the body.
How Caffeine Acts in the Body
Caffeine blocks adenosine receptors in the central nervous system. Adenosine is associated with feelings of fatigue and drowsiness. When its action is inhibited, there is an increase in alertness, improved focus, and a reduction in perceived exertion.
This reduction in perceived effort is extremely relevant in endurance sports. If an athlete feels that the effort is lower, they can sustain intensity for longer, even when physiological demand remains high.
In addition to its central effects, there is evidence of improved neuromuscular recruitment and enhanced muscle contraction efficiency, demonstrating that the impact is not merely subjective.
In Which Situations Does Caffeine Tend to Make the Biggest Difference?
The literature shows that the ergogenic effect is more evident in specific contexts, such as:
• long-distance events
• high-intensity training sessions
• final stages of competition
• situations of accumulated fatigue
In these scenarios, the modulation of central fatigue becomes decisive. Caffeine does not eliminate metabolic fatigue, but it alters how the brain interprets effort, allowing greater tolerance to discomfort.
What Do Studies Show in Practice?
Average performance gains range between 2% and 4%. In absolute terms, this may seem small, but in competitive settings, this difference can represent minutes in a marathon or decisive seconds in shorter events.
Much of this benefit is associated with the reduction in perceived exertion, but there is also influence on time to exhaustion, mean power output, and pace maintenance.
Dosage and Individual Variability
Evidence indicates that doses between 3 and 6 mg per kilogram of body weight are effective for improving performance. Higher doses do not necessarily increase the benefit and may raise the risk of adverse effects such as anxiety, tachycardia, and gastrointestinal discomfort.
The response to caffeine is individual. Genetic factors, habitual consumption, timing of ingestion, and type of exercise directly influence the outcome. Therefore, the strategy should be tested in training before being applied in competition.
So, Is It Just a Sensation or Real Performance Enhancement?
Sensation is part of the mechanism, but it is not illusory. The reduction in perceived exertion is a real neurophysiological phenomenon with measurable impact on performance.
Therefore, caffeine is not merely a psychological stimulus. It is an ergogenic aid with strong scientific support, capable of improving the ability to sustain intensity when used strategically.
WANG, Z.; QIU, B.; GAO, J.; DEL COSO, J. Effects of caffeine intake on endurance running performance and time to exhaustion: a systematic review and meta-analysis. Nutrients, v. 15, n. 1, p. 148, 2022. DOI: 10.3390/nu15010148.
