Caffeine stimulates the central nervous system by blocking adenosine, a neurotransmitter that normally causes a calming effect in the body. The resulting neural stimulation due to this blockage causes the adrenal glands to release adrenaline, the “fight or flight” hormone. Your heart rate increases, your pupils dilate, your muscles tighten up, and glucose is released into your blood stream for extra energy. Voila… you now have the caffeine buzz. But wait…we’re not done yet. Caffeine also increases dopamine. Dopamine activates the pleasure in parts of the brain. It has been suspected that this also contributes to caffeine addiction. Physiologically, caffeine makes us you feel alert, pumps adrenaline to give you energy and changes dopamine production to make you feel good.
In addition to various psychological and physiological benefits, numerous studies have documented caffeine’s ergogenic effect on athletic performance, particularly in regard to endurance. Studies show that caffeine ingestion prior to exercising extended endurance in moderately strenuous aerobic activity. Other studies researching caffeine consumption on elite distance runners and distance swimmers show increased performance times following caffeine consumption.
Despite effects on endurance, caffeine produced no effect on maximal muscular force in a study measuring voluntary and electrically stimulated muscle actions. However, the same study did show findings that suggest caffeine has an ergogenic effect on muscle during repetitive, low frequency stimulation.
Caffeine’s positive performance-enhancing effects have been well documented. So much so that the International Olympic Committee placed a ban leading to disqualification for an athlete with urinary limits exceeding 12 mg/mL. Roughly 600 to 800mg of caffeine, or 4 to 7 cups of coffee, consumed over a 30-minute period would be enough to exceed this level and cause disqualification. The National Collegiate Athletic Association has a similar limit, set at 15 mg/ml.
Scientists and many athletes have known for years, of course, that a cup of coffee before a workout jolts athletic performance, especially in endurance sports like distance running and cycling. Caffeine has been proven to increase the number of fatty acids circulating in the bloodstream, which enables people to run or pedal longer (since their muscles can absorb and burn that fat for fuel and save the body’s limited stores of carbohydrates until later in the workout). As a result, caffeine, which is legal under International Olympic Committee rules, is the most popular drug in sports.
More than two-thirds of about 20,680 Olympic athletes studied for a recent report had caffeine in their urine, with use highest among triathletes, cyclists and rowers. But whether and how caffeine affects other, less-aerobic activities, like weight training or playing a stop-and-go team sport like soccer or basketball, has been less clear.
So researchers at Coventry University in England recently recruited 13 fit young men and asked them to repeat a standard weight-training gym regimen on several occasions. An hour before one workout, the men consumed a sugar-free energy drink containing caffeine. An hour before another, they drank the same beverage, minus the caffeine. Then the men lifted, pressed and squatted, performing each exercise until they were exhausted.
Exhaustion arrived much later for those who’d had caffeine first. After swallowing the caffeinated beverage, the men completed significantly more repetitions of the exercises than after the placebo. They also reported feeling subjectively less tired during the entire bout and, in perhaps the most interesting finding, said that they were eager to repeat the whole workout again soon.
“Essentially, we found that with the caffeinated drink, the person felt more able to invest effort,” says Michael Duncan, a senior lecturer in sports science at the University of Exeter in England and lead author of the study. “They would put more work into the training session, and when the session was finished, in the presence of the caffeinated drink, they were more psychologically ready to go again.”
Instead, Dr. Duncan says, he believes that caffeine “antagonizes adenosine,” a substance in muscles that builds up during exercise and blunts the force of contractions. The more adenosine in a muscle, the less force it generates. Caffeine reduces adenosine levels, “which then enables more forceful muscular contractions and delays fatigue,” Dr. Duncan says. “That’s the theory, anyway,” he adds.
Please remember it is always advisable to consult your doctor or other qualified healthcare provider before undertaking any type of physical or increased exercise, and/or consuming coffee in relation to that exercise.
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