That's what researchers at the University of Georgia have found in a recent study exploring why muscles hurt during exercise. The research group previously learned that aspirin, though commonly used to treat muscle pain, did not reduce muscle pain produced by vigorous exercise.
"Muscle contractions produce a host of biochemicals that can stimulate pain. Aspirin blocks only one of those chemicals," said Patrick O'Connor, professor of exercise science in UGA's College of Education. "Apparently the biochemical blocked by aspirin has little role in exercise-induced muscle pain."
The researchers' latest study, published in the August issue of the Journal of Pain, found that caffeine reduced thigh muscle pain during cycling exercise. Participants in the study, 16 nonsmoking young adult men, cycled for 30 minutes on two separate days. The exercise intensity was the same on both days and purposefully set to make the riders' thigh muscles hurt. Participants in the study took either a caffeine pill or a placebo pill one hour before the exercise. The riders reported feeling substantially less pain in their thigh muscles after taking caffeine compared to after taking the placebo.
This observation suggests that prior reports showing that caffeine improves endurance exercise performance might be explained partially by caffeine's hypoalgesic properties, according to O'Connor.
"Not all analgesics or combinations [acetaminophine and caffeine] are effective for every type of pain or every individual," he said. "Much of this is due to biological variation among people in receptors for the drugs as well as variation in pain receptors in different body tissues. For instance, brain tissue has no pain receptors so surgery can be done on the brain without anesthesia. Of course it will hurt getting through the skin and cran
Contact: Michael Childs
University of Georgia