Caffeine is one of the most recognized and used ergogenic aids in the world thanks to its effects in improving performance in various sports modalities, being numerous meta-analyzes that indicate an improvement in resistance disciplines, muscular endurance, strength, power etc...
In most cases, doses of 3-6 mg / kg of caffeine exert their performance benefits through various mechanisms. One of them as an adenosine receptor antagonist (FIGURE 1), improving muscle activation, reducing the feeling of fatigue and pain. It is known that all these benefits together with its main side effects are dependent on various polymorphisms at the genetic level that are involved in the metabolization and its action at the level of adenosine receptors (CYP1A2, AHR and ADORA2A). In addition to other variables such as habituation to the consumption of this substance, form of intake (gum, drink, capsule ...), dose, sex, menstrual cycle, nutritional status and training, timing (time of intake) and other factors at the level epigenetic.
A potential mechanism that is currently under-explored is whether the bitter taste of caffeine mediates some of its ergogenic effects, since previous research has shown that bitter flavors (such as quinine) have the ability to improve performance and This fact is mediated by bitter taste receptors in the mouth and upper part of the gastrointestinal tract, although this may not occur at the same time.
In this way, some authors emphasize the possibility of an improvement in performance as it occurs in other similar strategies such as the use of menthol or carbohydrate rinsing where it seems that the sweet taste stimulates regions at the brain level through receptors of the oral cavity.
Some of the considerations of all this is that the intake of caffeine in liquid form (so that it has the same bitterness as quinine) is complicated to ingest due to its low palatability. On the other hand, drinks for athletes with caffeine or coffee do not have enough bitterness to cause such responses at the ergogenic level.
In addition, that it should be ingested and it is not enough just to rinse the mouth, since there are receptors at the level of the digestive tract that may be more important even than those in the mouth. With all this, we find quite a lot of controversies in the little existing literature, ruling out the improvement of performance directly with only rinses with caffeine solutions despite the existence of adenosine receptors in the mouth and this substance can be absorbed through the oral membrane
However, the explanation of all this could be the limited time (10 sec) that caffeine is in the oral cavity Vs at the intestinal level (45 min) so it would not give time to increase the concentration of plasma caffeine so Only using rinses.
On the other hand, other essays dedicated to evaluating reaction time, tasks at the cognitive level and their function during the performance of the activity if they have concluded with beneficial effects.
Anther point to add would be the knowledge of the interindividual variation on the ability to detect bitter flavors, which translates into the fact that the main ergogenic potential for a standardized dose of caffeine is due to differences in the taste response (there are genetically predisposed people “ TAS2R GENE ”with greater amount of receptors and greater sensitivity to bitter taste). Finally, it seems that some of the effects of improving the performance of caffeine could be driven by mere expectation or placebo (since, if an athlete gives something bitter and relates the taste to caffeine, knowing that caffeine improves the performance, it will improve without knowing that you have given him something that does not carry that substance).
To conclude, according to the authors about this hypothesis and together with other unresolved problems regarding the use of caffeine in sports, they suggest that it is tempting to believe that we know everything about caffeine as a performance enhancer, there is still a long way to go. Just by discovering some of the complexities surrounding the use of this substance, we have the potential to further improve the performance of our athletes over the next few years.