They signed up 25 fit, college-aged men to take part in experiments that required them to exercise. Some were regular caffeine users -- drinking the equivalent of four cups of coffee a day on average -- while others weren’t used to consuming much if any Joe.
The volunteers completed an initial exercise test on a stationary cycle to test for maximal oxygen consumption. Then they returned for two monitored, high-intensity, half-hour exercise sessions. Each session was separated by a week. The men were asked to refrain from caffeine, alcohol, and exercise prior to the testing days.
For one testing session, the men were given a placebo pill an hour prior to the high-intensity exercise. For the other session, men were given a caffeine pill (with the same amount of caffeine in 2.5 to 3 cups of coffee) prior to exercise.
The researchers, from the University of Illinois, questioned the men at regular intervals about their perceptions of quadriceps muscle pain, while they collected data on oxygen consumption, heart rate, and work rate.
The researchers found a statistically significant reduction in quadriceps muscle pain after giving the caffeine compared to the placebo pill. Both men accustomed to consuming caffeine and those who were not habitual caffeine drinkers demonstrated reduced pain with caffeine ingestion prior to exercise testing.
How Does Caffeine Reduce Muscle Pain?
Robert Motl, PhD, one of the researchers and a former competitive cyclist, says it’s become increasingly common for athletes to consume a variety of substances that include caffeine, motivated by “the notion that it will help you metabolize fat more readily.”
But that idea isn’t supported by compelling research, he says.
Motl, a professor of kinesiology and community health at the University of Illinois at Urbana-Champaign, says he had found in earlier research that caffeine affects a system in the brain and spinal cord involved in pain processing, which led him to speculate that it could reduce pain.
“What we saw [in this study] is something we didn’t expect,” he says in a news release. “Caffeine-naive individuals and habitual users have the same amount of reduction in pain during exercise after caffeine.”
More research, he says, might answer the question of whether a reduction in pain could result in an improvement in performance of athletes.
“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,” he says. “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.”