Why spit instead of swallow? The scientific explanation behind the habit that became a trend on World Cup pitches

Kevin Pina (6), from Cape Verde, during a hydration break
AP/Eric Gay)
In recent days, videos of players filling their mouths with a drink and then spitting it out, without swallowing, went viral during the 2026 World Cup. On social media, the gesture led to jokes and theories - from that it was water discarded due to excessive heat to speculation about a supposed "secret technique" for performance.
The scene is not exclusive to football: artists in long presentations also resort to similar gestures in short intervals, in a discreet way.
According to Fernando Valente, coordinator of the Diabetes Education Department of the Brazilian Diabetes Society (SBD) and director of the Diabetes Department of the Brazilian Society of Endocrinology and Metabology (SBEM), there is in fact a scientific strategy behind the gesture of spitting liquid - but it does not provide any extra calories to the athlete.
The technical name of the method is "carbohydrate mouth rinse", in scientific literature in English, and its effect, according to the specialist, occurs entirely in the head. Literally.
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The brain is tricked, not the body
According to Valente, the practice consists of keeping a carbohydrate-rich solution in the mouth for a few seconds - usually a sports drink concentrated in sugar and electrolytes - and then spitting it out, without swallowing.
Receptors present in the oral cavity identify the presence of carbohydrate and send signals to the central nervous system, stimulating brain areas linked to decision-making, motor control and executive functions, including the prefrontal cortex, a central region for cognitive performance during intense physical effort.
The practical result of this activation is a reduction in the perception of effort and a slight improvement in performance during high-intensity exercise. But the specialist makes a point of separating the sensation from the real fuel: the body does not receive any additional calories.
There is no ingestion, there is no digestion, there is no conversion into energy. What happens is that the brain interprets that there is fuel available and, based on this interpretation, allows the body to sustain a more intense effort - even without actually receiving glucose.
It is this dissociation between sensation and metabolic reality that explains why the technique works even when the athlete is already well fed.
According to Valente, if the athlete had a meal rich in carbohydrates before exercising, the mouthwash continues to produce the same effect - the mechanism depends on the sensory stimulus in the mouth, not the state the athlete's prior nutritional nutrition.
Renato Veiga (13), from Portugal, in the round of 16 match of the World Cup between Portugal and Spain
AP/Julio Cortez
A small but measurable gain
For recreational practitioners, the effect usually goes unnoticed: the performance gain is small and, in the daily lives of those who train for leisure, it may not make a noticeable difference.
The scenario changes when it comes to elite athletes, for whom fractions of a second separate results - like in a cycling time trial. In these contexts, even a small advantage can be decisive.
According to Valente, the performance improvement associated with the technique is around 1% to 3%. This is a modest number in everyday sports practice, but it is shown to be statistically significant in the clinical studies that tested the method - which supports its scientific validity, even though the effects are limited.
A systematic review published in Nutrients reinforces this pattern: when bringing together eleven studies on the subject, the authors found performance improvements in nine of them, with gains that varied from 1.5% to almost 12% in exercises of moderate to high intensity and lasting close to an hour - a range that encompasses the values cited by the specialist.
Most research on the topic has been conducted in cycling and running, with moderate to high intensity sessions lasting between 30 and 75 minutes.

It is this window of time that concentrates the best results demonstrated so far - a relevant fact to understand the limits of the technique when applied to other sports, such as football.
France players during a hydration break in the World Cup round of 16 match against Paraguay, in Philadelphia
AP/Matt Rourke)
And in a 90-minute match, does it make a difference?
A football match lasts 90 minutes and can extend even longer in the case of extra time -one half longer than the window in which carbohydrate mouthwash has demonstrated effectiveness in available scientific studies.
Still, Valente considers that the technique may make sense in specific moments of the match, and not throughout it as a whole.
For the specialist, the benefit tends to be concentrated in high-intensity phases and in the decisive moments of the game, when the athletes' perception of effort is higher - such as in ball disputes at the end of a balanced confrontation or in situations of extreme pressure.
Why spit instead of swallowing
For Valente, the main advantage of not ingesting the carbohydrate is to avoid gastrointestinal discomfort. In high-intensity exercises, ingesting liquids concentrated in sugar can generate nausea and a feeling of a full stomach, harming the performance that the athlete seeks to improve.
The mouthwash, in this sense, works as an alternative: it allows you to obtain part of the benefit of the perception of available energy without overloading the digestive system during physical effort.
When is it better to swallow the carbohydrate
The technique has clear limits, according to the specialist. If the athlete's glycogen reserves are already very low - which usually occurs during very prolonged exercise -, just gulping down the drink won't do the trick, because at that moment the muscle needs a real supply of energy arriving through the bloodstream. This is when effective carbohydrate intake becomes important: the body can no longer be satisfied with the perception of fuel, but actually needs it.
Valente reinforces that swallowing the drink also remains the most recommended strategy in exercises lasting over 75 minutes, or in any situation in which the body already demands real additional energy - scenarios in which glycogen replacement is no longer optional.
Not all spit is carbohydrate mouthwash
Despite the repercussion on social media, Valente avoids claiming that the players caught in videos during the World Cup are necessarily applying this strategy. According to him, the gesture of spitting can have much simpler explanations - from habit and discomfort in the mouth to the simple ingestion or disposal of water during the game. Confirmation that it is indeed carbohydrate mouthwash, according to the expert, would only be possible with information from the teams themselves or the athletes involved.
"Although the technique really exists and it is scientifically valid", says Valente, this does not allow us to conclude that every player caught spitting on the field is using it - even if the proven effects of the method, even if small, are real and measurable.

Source: G1

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