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NEW YORK - That morning cup of coffee may help ease post-exercise muscle soreness, if preliminary research is correct.

A worker pumps coffee at a coffee shop in Taipei August 3, 2006. In a small study of female college students, researchers found that a caffeine supplement seemed to lessen the muscle pain that crops up a day after a challenging workout. [Reuters]

In a small study of female college students, researchers found that a caffeine supplement seemed to lessen the muscle pain that crops up a day after a challenging workout.

Known as delayed-onset muscle soreness, the pain is common a day or two after a workout that was more intense than normal. Exercise that involves eccentric contraction of the muscles is particularly likely to cause delayed muscle pain.

In eccentric contraction, the muscle produces a force while it's being lengthened. This happens when a person runs downhill, for example, or lowers a weight during a bicep curl.

Exercisers and researchers alike have tried many ways to prevent this post-exercise soreness, including over-the-counter painkillers, stretching and massage -- but studies have found no cure-all for the problem.

In the current study, published in the Journal of Pain, researchers at the University of Georgia in Athens looked at the effects of a caffeine supplement on delayed muscle pain in nine young women.

First, in a simulated workout, the researchers used electrical stimulation to produce eccentric contractions in the women's thigh muscles -- enough to cause moderate day-after soreness.

Next, they repeated the procedure over the next two days, but on each day, the women took either a caffeine pill or placebo pill one hour before the muscle workout. Neither the women nor the researchers knew which pill was given on which day.

Overall, the women reported significantly less muscle soreness during the workout when they took caffeine instead of the placebo. The supplement had about the amount of caffeine found in two cups of coffee.

The theory is that caffeine eases delayed muscle pain by blocking the activity of a chemical called adenosine, which is released as part of the inflammatory response to injury. Adenosine can activate pain receptors in body cells, explained Victor Maridakis, the study's lead author.

But before downing a couple of cups of coffee before your workout Maridakis recommends careful consideration of the possible side effects of caffeine.

"The negative side effects of caffeine are increased feelings of anxiety, heart palpitations, increased blood pressure, upset stomach, increased urination and disrupted sleep," he said.

"Caution should be used when consuming caffeine so not to exacerbate these side effects."