"The results of this experiment add to the body of evidence suggesting that caffeine ingestion influences muscle pain during exercise and provides novel evidence that caffeine is associated with a reduction in muscle pain in both habitual users and nonusers of caffeine."—Robert W. Motl, PhD
Caffeine is a double-edged sword when it comes to health. Some studies suggest that caffeine consumption can reduce the risk of gouty arthritis and/or Parkinson’s disease, for example, while others show that caffeine can increase risk of osteoporosis. “The results of this experiment add to the body of evidence suggesting that caffeine ingestion influences muscle pain during exercise and provides novel evidence that caffeine is associated with a reduction in muscle pain in both habitual users and nonusers of caffeine,” said Robert W. Motl, PhD, a professor of kinesiology and community health at the University of Illinois at Urbana-Champaign.
The new study was comprised of 25 college-aged males who were divided into 2 groups. One group consumed a very low to non-existent amount of caffeine daily and the other group consumed about 400 milligrams of caffeine a day, which is the equivalent of 3 to 4 cups of coffee. Participants completed an initial exercise test on an ergometer to determine their maximal oxygen consumption. Next, they completed 2 high-intensity, 30-minute exercise sessions. The participants were given a pill 1 hour before exercise testing. On one occasion, the pill contained a dose of caffeine measuring 5 milligrams per kilogram of body weight, which is equal to 2 to 3 cups of coffee. On the next occasion, participants received a placebo. All participants were told not to consume caffeine before the experiment. Researchers recorded subjects’ perceptions of quadriceps muscle pain at regular intervals, along with data on oxygen consumption, heart rate and work rate, during both exercise periods.
Caffeine conundrum: tolerance doesn’t affect pain perception
“Caffeine-naïve individuals and habitual users have the same amount of reduction in pain during exercise after caffeine (consumption),” Dr. Motl said in a press release.
Exactly why this occurs is unclear. “If you regularly consume caffeine, you have to have more to have that bigger, mental-energy effect, [b]ut the tolerance effect is not ubiquitous across all stimuli.”
He said that even brain metabolism doesn’t show this tolerance-type effect. “[W]ith individuals who are habitual users versus non-habitual users, if you give them caffeine and do brain imaging, the activation is identical,” Dr. Motl said. “It’s really interesting why some processes show tolerance and others don’t.”
Or, he speculated, “it may just be that pain during exercise doesn’t show tolerance effects to caffeine.”
Exactly how caffeine can block pain from exercise is not fully understood, but it may block adenosine.
Going forward, Dr. Motl plans to conduct rodent studies to further elucidate how caffeine may reduce pain. “If we can get at the biological mechanism, we can begin to understand why there may or may not be this kind of tolerance,” he said.
Moreover, “additional research might examine the role of varying doses of caffeine on muscle pain during high-intensity exercise in individuals who differ in habitual caffeine consumption, the interactive effects of caffeine with other analgesic substances and mechanisms that might explain the effect of caffeine on muscle pain during exercise,” he said.
Caffeine and exercise: Translating research into practice
This research will likely help shed light on how and if caffeine affects sport performance.
“One of the things that may be a practical application, is if you go to the gym and you exercise and it hurts, you may be prone to stop doing that because pain is an aversive stimulus that tells you to withdraw,” Dr. Motl said. “So if we could give people a little caffeine and reduce the amount of pain they’re experiencing, maybe that would help them stick with that exercise,” he said, adding that “maybe then they’ll push a little harder as well…maybe get even better adaptations to the exercise.”
References
1. Gliottoni RC, Meuers JR, Arngrímsson SÁ, et al. Effect of caffeine on quadriceps muscle pain during acute cycling exerciuse in low versus high caffeine consumption. International Journal of Sport Nutrition and Exercise Metabolism. 2009;19:150-161.
PubMed: Related Articles