Healthnotes Newswire (February 15, 2007)—If you don’t drink caffeinated beverages every day, it might do you good to have some the day after an overly vigorous workout: a new study suggests that caffeine can relieve pain that sets in a day or two after exercise injury.

Caffeine is a plant chemical that is best known for its action as a nervous system stimulant. It can cause side effects such as restlessness, irritability, insomnia, and gastrointestinal upset in some people. It is safe for most people, however, and if future studies confirm these findings, it could be a reasonable treatment option for people who experience skeletal muscle pain after engaging in unusually intense exercise that involves eccentric muscle activity.

Caffeine’s pain-relieving effects are well documented. In previous studies, caffeine has reduced forearm and leg muscle pain, and prevented angina pain, during exercise. Other studies have found that caffeine can increase stamina and the strength of muscle contractions during exercise.

But the pain and weakness from overexercising are often delayed. Muscle injuries from exercise trigger an inflammatory response that might cause pain that sets in hours later.

The Journal of Pain published the results of new study, which looked at caffeine’s effects on delayed-onset muscle pain and strength one and two days after muscle injury. Nine female college students who habitually consumed only small amounts of caffeine and did not participate in regular intense exercise were recruited for the study.

After being tested for leg muscle strength and pain sensation during strong leg muscle contractions, the students’ leg muscles were damaged using electrically induced “eccentric” exercises. Eccentric exercise occurs when skeletal muscles produce force while being lengthened. For example, when going into a squat very slowly; the muscles that resist your going down are doing eccentric exercise.

Two exercises were performed 24 and 48 hours after the injury. The women performed a maximal (using all of their strength) and submaximal (less than full-strength) contraction of the injured muscle before and then one hour after taking either caffeine or placebo. The amount of caffeine used in the study (5 mg per kilogram of body weight, about 300 mg for an average woman) could be found in two cups of coffee, an amount that is part of many people’s daily diet.

A large decrease in muscle pain during testing—almost 48%—was reported after caffeine ingestion compared with placebo. Muscle strength increased slightly (4.4%) after caffeine as well.

“Based on this study, caffeine can reduce the skeletal muscle pain that occurs 24 to 48 hours following a bout of unusually intense eccentric exercise by as much as 48%,” commented Victor Maridakis, a researcher at the University of Georgia and the lead author of the study. “This particular muscle pain is characterized by pain or discomfort in muscles during movements that aren’t normally painful, or a sensitivity of muscles to even the slightest of movements.” He added that, while a common pulled or strained muscle may share similar aspects of delayed-onset muscle pain, more research would be needed to determine the effect of caffeine after these types of injuries.

Because the women in the study weren’t regular caffeine drinkers and were not involved in frequent intense exercise, it is hard to say from these findings whether caffeine could be useful to people who drink coffee or tea regularly, or to athletes who want to continue to perform one or two days after a muscle injury.

(J Pain 2006;Dec 8 [e-pub ahead of print])