Researches show that caffeine has a positive affect on physical activity – how does it happen?
What's caffeine?
Caffeine is the most popular drug in the world. Today, when the market in flooded with many nutrition supplements, the caffeine is still considered among the most common nutrition supplements from a few reasons: it fits for a variety of work-outs (endurance and strength), it's cheap, it's legal and it has minimal side-affects.
Not just in coffee
The caffeine can be found in over 60 mini-plants in the world: seeds, leaves, fruits and so on, but we know it mostly in drinks like coffee, tea, sodas, energy drinks, foods like chocolate or a variety of medications or nutrition supplements that contain it.
Caffeine and exercise
Many researches investigated the affect of caffeine on physical exercise. The first research was done in 1907, and checked the influence of adding 500 mg or caffeine on lifting weight using the finger. It has been found that adding caffeine increases the finger's ability to lift weight.
In a research done in the late 70's, the affect of caffeine consumption (10 mg per 1 kg) was tested on long distance runners. The caffeine was consumed near the beginning of the run. The runners have improved their results by 1.9% in comparison to the control group.
Caffeine consumption in the quantity of 3-9 mg per 1 kg, or a total of 250 mg caffeine an hour before the work-out, was found contributing to the length and intensity of the work-out.
Mechanism
The caffeine is absorbed quickly in the digestive system, when the peak of its blood consecration arrived an hour later. The caffeine is also secreted from the body quickly: within 3-6 hours the caffeine level in the blood drops by half.
The influence of the caffeine on physical exercise relies on the use of fat as a source of energy, what leads to "glycogen sparing affect" save of glycogen in the muscle, which is a limited source of energy, in the arousal of the central nervous system and decreasing the feeling of pain during effort.
The influence of caffeine is inconsistent and low among people who eat a lot of carbohydrates. In addition, there are different groups in the population, which have different sensitivity and tolerance to caffeine and hormone secrete after caffeine consumption.
It has been found that athletes who consume caffeine every day do not enjoy the benefits of caffeine on their performances, in comparison to athletes who consumed caffeine only a day before competing. In addition, avoiding caffeine 4-6 days before the competition increases its effectiveness.
Does the way we consume caffeine has an influence?
The influence of caffeine consumed in coffee drinks, for instance, is lower in comparison to caffeine consumed in a tabulate. The reason for that might be other components in the coffee, which decrease the influence of the caffeine.
Caffeine – legal for athletes
In the past, caffeine was forbidden for use by the rules of the international Olympic committee: an athlete that too much caffeine was found in his body was considered as one who took illegal incentive, and was punished accordingly. In a decision taken by the WADA (world anti doping association), caffeine was dropped out of the forbidden drugs list, and starting January 2004 – it was no longer forbidden for Olympic athletes.
It's important to know
People that are not used to consume caffeine might suffer from side-affects while consuming it higher than 1.5 grams per 1 kg. In these cases one might suffer from symptoms such as headaches, unrest, insomnia, spasms, nerves, shakes, higher heart rate and higher blood pressure.
In addition, caffeine is diuretic, and many articles mention it might cause a negative balance of fluids. The diuretic affect of caffeine is most likely smaller when it is consumed with fluids during physical exercise, since during exercise the body secretes hormones that decrease the blood flow to the kidneys. A moderate consumption of caffeine (300 mg a day) won't lead to any side affects.
|
The food/drink |
Caffeine amount |
|
coffee |
75 mg per a 190 ml cup |
|
Filter coffee/espresso |
100-180 mg per 190 ml cup |
|
Decaf coffee |
4 mg per a 190 ml cup |
|
Tea |
15-110 mg per 190 ml cup |
|
Chocolate drinks (from prouder) |
1/1-8/2 mg per 200 ml cup |
|
Energy drinks or guarana |
28-87 mg per 250 ml can |
|
Cola (diet or regular) |
10-70 mg per 330 ml can |
|
Chocolate |
6-40 mg per 50 grams |
Dr. Naama Constantini, M.D., a family physician, chairman of the medical commission of Israel's Olympics team and head of sports medicine at Hadassah Optimal.
Rakefet Arieli, clinical nutritionist, Hadassah Optimal, Sports Medicine Center.