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September 20, 2016 23:06

Caffeine

main functions caffeine

  • Increases energy production.
  • increases fat loss.
  • Increases endurance.

mechanism of action of caffeine

Caffeine is used for hundreds of years.Although it is not a nutrient, but is widely used in usual diets.During metabolism in the liver is converted into three theobromine - paraxanthine, theophylline and theobromine.

proposed three main theories for the ergogenic effect of caffeine.

  • Being a CNS stimulant, reduces the perception of fatigue.
  • Enhances muscle contraction due to the beneficial effects on ion transport.
  • Enhances fat utilization and thus saves glycogen muscle.Since

caffeine enters the central nervous system and skeletal muscles, it is impossible to separate it from the effect on the CNS effects on the peripheral nervous system.Possibly in different situations are responsible for the improvement in various arrangements.

results

research interest in the caffeine as a ergogenic agent arose due Costill lab work more than 40 years ago.In a study in 197

8 of nine competing cyclists took 330 mg of caffeine (5 mg kg-1) for 1 hour prior to the race at 80% V02max and were able to participate in the race to failure by 19% longer (90 minutes compared to 75 minutes).

A study conducted in 1979 showed that 250 mg of caffeine consumption has increased by 20% the amount of work that can be done in 2 hours. The two studies showed that in experiments with caffeine fat utilization for the release of energy increased by aboutthirty %.G. study in 1980 found that the consumption of caffeine 5 mg kg-1, reduces the use of muscle glycogen by 42% and increases muscle triglyceride use 150% within 30 minutes of cycling at 70% V02max.

Subsequent experiments on caffeine and indicators of physical activity gave conflicting results.However, in the past 10 years, it found that caffeine can improve endurance.

In 1991, Graham, Spriet evaluated the effect of caffeine on cyclists and runners.Athletes took 9 mg of caffeine-kg-1 for 1 hour before cycling and running to exhaustion at an intensity of about 85% V02max.The average increase in endurance run was 44%, while in cycling - 51%.However caffeine levels in four of the 12 urine samples gave figures, similar or higher than the threshold set by IOC.

Graham, Spriet conducted another study to investigate the effect of different doses of caffeine on the well-trained athletes.Eight subjects avoided caffeine for 48 hours, then the consumed 3, 6 and 9 mg of caffeine per 1 kg of body weight or placebo for 1 h before loading at 85% V02max.Endurance increased at doses of 3 and 6 mg kg-1 but not at a dose of 9 mg-1 g.increased plasma epinephrine not at 3 mg dose but increased at higher doses.Only the dose of 9 mg revealed increasing levels of glycerol and free fatty acids.

These data indicate that even the lowest dose - 3 mg kg-1 - shows ergogenic effect, without increasing levels of epinephrine.

Recommendations on the use of caffeine

Graham, Spriet believe that consumption of 3-13 mg of caffeine-kg-1 increases endurance by 20-50% in elite athletes and fans during a cycling or running at 80-90% V02max.

They point out that the dose of caffeine from 3 to 6 mg kg-1 for 1 h to give the ergogenic effect of the load without raising the level of caffeine in the urine above the IOC doping threshold.

Although higher doses of caffeine from 9 to 13 mg kg-1 also improve athletic performance, they are likely to cause side effects and raise the level of caffeine in the urine above the IOC doping threshold (12 ICGdl-1) and HCCA (15 mg dL-1).

When the relative safety of caffeine, high doses it can cause side effects, including nausea, muscle tremors, rapid pulse and headaches.Athletes who are sensitive to caffeine may experience these symptoms even at low doses it.

Athletes should be aware that the ergogenic effects of some proprietary additives may be the result of caffeine contained in them.Nuts, Paraguayan tea and guarana contain caffeine.