Caffeine-naive individuals and habitual users have the same amount of reduction in pain during exercise after caffeine consumption, U.S. researchers say.

University of Illinois kinesiology and community health professor Robert Motl said the study's 25 participants were fit, college-age males divided into two distinct groups -- subjects whose everyday caffeine consumption was extremely low to non-existent and those with an average caffeine intake of about 400 milligrams a day -- the equivalent of three to four cups of coffee.

After completing an initial exercise test in the lab on an ergometer, or stationary cycle, subjects returned for two monitored high-intensity, 30-minute exercise sessions.

An hour prior to each session, cyclists, who had been instructed not to consume caffeine during the prior 24-hour period, were given a pill. On one occasion, it contained a dose of caffeine measuring 5 milligrams per kilogram of body weight -- equivalent to two to three cups of coffee; the other time, they received a placebo.

"What's interesting, is that when we found that caffeine tolerance doesn't matter, we were perplexed at first," Motl said in a statement. "Then we looked at reviews of the literature relative to caffeine and tolerance effects across a variety of other stimuli. Sometimes you see them, sometimes you don't. That is, sometimes regular caffeine use is associated with a smaller response, whereas, other times, it's not."

The findings are published in the April edition of the International Journal of Sport Nutrition and Exercise Metabolism.