Caffeine belongs chemically to a group of substances called "purines" (the chemical term is 1,3,7-trimethylxanthine), naturally occurring in coffee beans, tea leaves, chocolate, cocoa and cola seeds (an African plant).
Caffeine is often added to fizzy drinks and many nonprescription drugs or supplements. In nature there are sixty-three species of plants containing caffeine.
Effects of caffeine
Although the ergogenic effects of caffeine have not yet been fully understood, it now seems certain that they are mediated by the release of catecholamines. These hormones are called adrenaline and noradrenaline or epinephrine and norepinephrine respectively. Their action, maximum during a sudden and intense fright or effort, acts both centrally and peripherally. To prepare the body to support this great psychophysical commitment, catecholamines:
- increase coronary flow (increased blood supply to the heart)
- increase cardiac output (increased blood supply to tissues)
- they increase systolic blood pressure
- they increase the muscular, renal and cutaneous blood flow
- increase metabolism
- they increase glucose production (glycogenolysis) and lipolysis
- block the adenosine receptors of adipose and nerve cells (lipolytic and stimulating effect)
Diet and caffeine
In the United States, 45% of the caffeine consumed comes from coffee other important food sources of caffeine are represented by tea, cola-type drinks, energy drinks, medicines (diuretics, slimming and painkillers in the first place).
Average caffeine content in commonly used beverages
PLEASE NOTE: in athletes it is necessary to take into account the summation effect of the caffeine taken with the various foods so as not to exceed the limits imposed by the anti-doping regulations.
The caffeine content of traditional mocha coffee is higher than that of espresso
In women, the use of some contraceptives (ethinyl estradiol) increases the duration of action of caffeine by about 50%.
Some drugs have a high caffeine content (100-200 mg per tablet)
Diet is able to influence the individual response to caffeine. The different sensitivity towards this substance could therefore also be explained by analyzing the eating habits of those who take it. It has been seen, for example, that the caffeine present in coffee has a lower ergogenic efficacy than that sold in tablets. The mobilization of fats deriving from the ingestion of caffeine is lower in subjects who consume high quantities of carbohydrates in the pre-pre-race meal. The addiction to the substance is also very important, the process by which the organism develops a sort of resistance towards its pharmacological action. To maximize the ergogenic effects of caffeine, the athlete should therefore refrain from consuming caffeinated foods, drugs and beverages in the four to six days preceding the competition.
The word to science
Although not all studies confirm the ergogenic effects of caffeine, most of them enhance these characteristics, even at low doses. Let's see some of them:
in one study, some athletes who consumed caffeine at high doses (10 mg / kg body weight) performed 19% better than other athletes treated with placebo or under control conditions. The test consisted of a treadmill exercise that continued until physical exhaustion.
Other studies have shown that the maximum ergogenic effect of caffeine is obtainable through dosages in the order of 5 mg / kg. At these doses, the concentration of caffeine in the urine was even lower than the limits imposed by the IOC.
Higher quantities do not appear to bring significant improvements in athletic performance.
The effects of caffeine on the muscular system are maximal for medium intensity exercises. Conversely, no positive effect on maximal power or strength has been demonstrated.
Caffeine intake
To maximize the positive effects, it is recommended to take 3 to 6 mg of caffeine per kg of body weight, 180 to 75 minutes before the sporting competition. Small doses can also be taken during endurance performances, for example in view of the finish line.
Considering the great individual variability, it is a good idea to experiment with the use of caffeine in training, avoiding taking it in the three days preceding the competition. Because of the possible side effects it is recommended to consult a doctor before use.
Doping controls
Due to its ergogenic effects, caffeine cannot be freely consumed by athletes. The anti-doping authorities have in fact set limits on intake, beyond which the use of this substance is considered doping and as such punished with the disqualification of the athlete.
A subject tests positive for doping controls when the concentration of caffeine in the urine exceeds 0.012 mg / ml (= 12mcg / ml) *. It is not easy to establish exactly what the intake dose is capable of exceeding this threshold, since caffeine is metabolized by the liver at different rates from individual to individual (a bit like alcohol). This limit value can be reached, broadly speaking, by consuming 800-1200 mg of pure caffeine or 8 cups of strong coffee.
For this reason it is advisable not to exceed 6-8 cups of espresso or two-three cups of traditional coffee in the three hours prior to the competition. It is also important to pay particular attention to the possible additive effect (simultaneous intake of energy drinks, coffee and drugs or other caffeine-based drinks).
* These values may vary slightly depending on the sports federation to which they belong
Side effects
In the case of doses higher than 500-1000 mg, heart rhythm alterations may also appear (tachycardia and ventricular extrasystole). The LD-50 of caffeine (lethal quantity for 50% of the population) corresponds to 150 mg / kg of weight, well thirty times above the recommended values.
