The use of caffeine in sport
[This article has been translated Google]
Caffeine is a substance that enjoys social acceptance and widespread use throughout the world. Unlike many other psychoactive substances, it is legal. Its action has a stimulating effect on the central nervous system (1) which results in arousal, increased energy, improved concentration, cognitive abilities, memory of reaction time, etc.
From a chemical point of view, caffeine is a bitter, white, crystalline purine, methylxanthine alkaloid, and is chemically related to the principles of adenine and guanine of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main sources of caffeine in the diet are: coffee, tea, chocolate, Coca-Cola and energy drinks. The caffeine content of these products ranges from 30-200 mg per serving, with caffeine-containing supplements usually delivering doses from 100 to 200 mg per serving. In 2004, WADA removed caffeine from the list of prohibited substances in sport, and therefore there was a rapid increase in its consumption among athletes in order to achieve ergogenic effects. The Australian Sports Institute qualifies caffeine for Group A supplements, i.e. those with scientifically proven effectiveness. The influence of caffeine on athletic performance has been the subject of research since the beginning of the 20th century (Rivers 1907). It is worth specifying comprehensive reviews in scientific papers: Graham (2001), Doherty and Smith (2004, 2005), Burke (2008, 2013).
The comprehensive action of caffeine on the human body has been extensively studied. It takes place mainly through interaction with adenosine receptors (2, 3). Caffeine is an antagonist of A1 and A2a receptors, which initiates a cascade of metabolic changes in the body such as: increase in the level of monoamines (adrenaline, noradrenaline), phosphodiesterase inhibition, acetylcholinesterase inhibition, increase in dopamine signaling in some brain regions, increase in glutamate levels (3). Caffeine also has a number of activities within the skeletal muscles such as the effect on calcium transport, potassium sodium pump activity, cAMP increase, and the effect on glycogen phosphorylase activity. The increase in cAMP and catecholamines stimulates lipolysis in adipocytes and skeletal muscles, increasing the level of free fatty acids in the blood and the availability of intramuscular triglycerides (IMTG). However, the effects on the sports results are mainly due to effects on the central nervous system and adenosine receptors, which results in reduced fatigue and increased recruitment of motor units. Caffeine metabolites (paraxanthin, theophylline, theobromine) also exert an independent effect on the body. Paraxanthin stimulates lipolysis, theobromine widens blood vessels and increases diuresis, theophylline relaxes smooth muscles.
Side effects of excessive caffeine intake may include: irritation, anxiety, headache, overstimulation, excess catecholamines and hypercortisolism, disturbed heart rhythm, diuresis, insomnia, headaches, “scars in front of eyes”, delirium, tinnitus. Most often, side effects occur in the case of daily supply above 6-9 mg / kg m.c. Each person has an individual caffeine metabolism, depends on factors such as: genetic polymorphisms of enzymes responsible for hepatic caffeine metabolism (CYP1A2, AHR), polymorphisms of genes coding for adenosine receptor functions (ADORA2A), liver condition, frequency of supply of caffeine in the form of a supplement or food products (36).
The most fascinating thing about caffeine is that it can improve athletic performance in practically any type of discipline. There is evidence that competitors participating in monotonous efforts, lasting 30-60 minutes and over 90 minutes, i.e. Endurance sports benefit from caffeine supplementation (4, 5, 6, 7). There is evidence of the benefits of taking caffeine among team athletes, for example in football, rugby, volleyball, hockey (8, 9, 10, 11, 12, 13), in tennis (14), golf (15) and many others .
It has been proven that caffeine can improve reaction time in combat sports (16) and average and peak power during the Wingate test. It has been shown that caffeine also improves athletic performance in disciplines where competitors compete from 1 to 30 minutes, and the effort is intense for example in swimming (17), in rowing (18), track cycling (19), medium-distance runs (20 ). It has also been proven that caffeine may slightly improve the sports score in speed disciplines with very high intensity of effort (47). The only disciplines in which caffeine does not seem to improve the sports result are individual high intensity efforts such as jumps, sprints, throws, weightlifting, although athletes of these disciplines can benefit in the case of repeated repetition of activities performed during competitions (21 ). The main factor supporting the sports result during caffeine supplementation is the inhibition of fatigue during physical exercise.
A lot of research has been done on athletes to optimize the dose of caffeine supplementation for ergogenic purposes. Doses of the order of 6 mg / kg and 9 mg / kg m. C. Have been shown to provide similar benefits to the test of time during intense physical exercise (18). In long-term efforts (over 1 hour), similar benefits were noted at doses of 5, 9 and 13 mg / kg m. C. (22) and 3 and 6 mg / kg m. C. (23). The next study reported that the caffeine dose threshold, which improves the cycling test time, is 3.2 mg / kg m. C. (5). In yet another trial, it was shown that 1-2 mg / kg m.c. caffeine improved the time trial at the end of a 2-hour cycling ride as well as 6 mg / kg m. c. (4). It has also been shown that high doses of caffeine (9 mg / kg m. C.) May reduce the strength compared to the lower doses (23). Many scientific works determine the effective dose of caffeine at 3 mg / kg m.c. The goal of effective caffeine supplementation should be to adjust the appropriate dose for the individual. The portion should bring as many benefits as possible with the minimum of side effects, what should be determined with the player on the training, by trial and error. It seems that the optimal dose of caffeine oscillates between 3-6 mg / kg, however, those who are susceptible to its action may also find lower doses of 1-3 mg / kg, and some individuals may require doses above 6 mg / kg mc.
Caffeine is rapidly absorbed and reaches maximum concentration in blood after 1 hour of intake. It is slowly catabolized, its half-life is from 4 to 6 hours for most people. The highest concentration persists 3-4 hours after ingestion (3). The ergogenic effects of caffeine can persist up to 6 hours after ingestion, even after an exhaustive exercise (24). By default, caffeine is recommended 1 hour before planned physical activity. In long-term efforts, taking caffeine during, for example, an energy gel may bring additional benefits (4, 5, 25, 26). Similar benefits (3% improvement in time sample) were shown when 6 caffeine doses were administered at 1 mg / kg every 15 minutes during a 2-hour trial, a single dose of 6 mg / kg 1 hour before the activity and a small dose dose (approximately 1.5 mg / kg) over the last 40 minutes of the trial. Probably participants were sensitized to low doses of caffeine when they began to feel strong tiredness (4).
Due to the common consumption of coffee as a source of caffeine, studies have been carried out to verify the impact of coffee consumption on sports performance. Some of these studies have shown that coffee can be ergogenic (27, 28, 29, 41), others question this thesis (30, 31, 32). Only two studies compared the effect of coffee and anhydrous caffeine on the sports score. Graham et al. Showed that runners on the treadmill no longer experienced fatigue after consuming pure caffeine for the same amount of caffeine from coffee. Differences in the impact on exercise tolerance occurred despite the standardization of the caffeine content and its metabolites in both trials. It has been suggested that other substances in coffee may counteract the erogenous action of caffeine. Mclellan and Bell showed, however, that the consumption of one cup of regular coffee and decaffeinated coffee before consuming anhydrous caffeine did not adversely affect the beneficial effects of caffeine. More research is needed to compare the beneficial effects of anhydrous caffeine to natural sources such as from coffee beans. Remember that coffee contains substances such as: chlorogenic acid, other antioxidants (polyphenols), vitamins (in particular b3), minerals (mainly magnesium, potassium) and many other chemicals that can modulate the effects of caffeine. The most important reason why coffee should not be treated as a sure ergogenik, eg before a competition, is the fact that the content of coffee in brew is always unknown. It depends on many factors, such as the type of grains (eg country of origin, method of treatment), length and temperature of grain burning, thickness of grinding grains before brewing, water temperature during brewing, extraction method and, first of all, water contact with grains during extraction (the longer the contact of grains with water, the more caffeine in the infusion). In one espresso, the caffeine content may vary between 25-214 mg per serving (33). Coffee brewed with alternative gravity methods, eg drip, chemex, aeropress, contain much higher amounts of caffeine and in my opinion they are much more advantageous as ergogenics. It is also worth mentioning the pro-health properties of coffee, which is summarized by Grosso’s work from 2017 (54). Research findings and meta-analyzes indicate that coffee is associated with a probable reduction in the risk of breast, colon, endometrial and prostate cancer, cardiovascular disease, mortality, Parkinson’s and type 2 diabetes. Caffeine has been associated with a probable reduction in the risk of Parkinson’s disease and type-1 diabetes 2.
In addition, a number of studies verifying the use of alternative sources of caffeine such as energy drinks, Coca-cola, caffeine gums were carried out, but I will present a summary in a separate article. It is only worth mentioning that the consumption of caffeine gum causes a rapid, rapid increase in caffeine in the plasma by its absorption in the mouth (21, 34, 35).
Most athletes limit caffeine intake 24-48 before competition. However, there were no differences between the effectiveness of caffeine in regular users and those using it sporadically or taking their breaks (37). A study in which the effects of caffeine on a 1-hour cycling test were checked, after a break in its supply lasting 4 days or without a break, showed that 3 mg / kc m. C. Caffeine improved the result regardless of the preparation (38). Avoiding caffeine before an exercise test can be associated with side effects such as headaches and fatigue. In fact, there are suggestions that the benefits of caffeine intake seen in controlled trials may be overstated due to the reversal of adverse withdrawal symptoms rather than the ergogenic effect of caffeine per se (39). Caffeine withdrawal may also cause side effects similar to its overdose in the event of reincorporation.
In summary, caffeine is a substance commonly used to increase cognitive ability, alertness, reaction time, reduce fatigue and has proven ergogenic properties in many sports. It has been proven that a beneficial effect can be achieved already at doses of 1-3 mg / kg m. C., However, the standard, recommended, effective dose is 3-6 mg / kg m. C. And from the lower values of this ceiling, I would advise you to start your adventure with caffeine supplementation. Doses of 6-9 mg / kg m. C. May be more effective in some people, but they will lead to symptoms of caffeine overdose, which may weaken both cognitive and athletic performance. Due to the individual, variable metabolism of caffeine, I suggest to adjust the appropriate dose for the individual by trial and error during the training. Depending on the purpose, a combination of caffeine supplementation with another synergistic substance, eg l-theanine, forskolin, acetylcholinergics (alpha GPC, CDP choline, huperzin, galantamine), adaptogens or other nootropic substances, should be considered. The safe, gold nootropic standard is the combination of caffeine and l-theanine, preferably in the ratio of 1: 2, which is confirmed by many studies (48, 49, 50, 51, 52, 53). In the next article, I will break down the application of l-theanine to the first.
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