Muscles feeling sore?

Post-workout euphoria can leave you feeling pumped to conquer the world -- until the next morning, when you can barely walk to the bathroom or lift an arm to brush your teeth.

Such are the painful rewards of delayed onset muscle soreness (DOMS), a result of microscopic tears to muscle fibers that occur when you run faster, lunge deeper, crunch harder or lift more than usual. The damage ignites an inflammatory response as the muscle repairs itself, causing pain that peaks 24 to 48 hours after the activity and dissipates in five to seven days, said Carol Torgan, a health consultant and fellow with the American College of Sports Medicine.

Contrary to popular belief, next-day soreness is not caused by a buildup of lactic acid, a normal byproduct of muscle metabolism responsible for the burn you feel during exercise, Torgan said. Lactic acid quickly leaves your muscles afterward, she said.

DOMS is most common after a new activity or exercises involving "eccentric muscle contractions," which is when the muscle lengthens as it contracts, such as when you lower the weight in bicep curls or run downhill, Torgan said.

Next-day soreness is usually a good thing. The tear-and-repair process forces the muscle to adapt, so that the next time you do the same exercise there's less damage, less soreness and less recovery time -- basically, you're stronger.

"If you don't get muscle damage, you don't get muscle growth," said Dr. Gabe Mirkin, a retired physician who runs a health news website (www.drmirkin.com). "If you want to grow and gain strength, you have to get sore."

Here's how to handle DOMS:

Sore muscles heal faster if you just rest, but when you exert slight pressure on sore muscles, such as through light running, biking or very light weight lifting, you cause the muscle fibers to become more fibrous, so they can later withstand greater stress during your harder workouts, he said. It's a delicate balance.

No one knows for sure how much damage is necessary to get the muscle to adapt, said Priscilla Clarkson, distinguished professor of kinesiology at University of Massachusetts at Amherst, but she said some soreness is probably optimal. Too much soreness can be counterproductive, because the longer it takes for the muscles to rebuild, the longer you have to wait to resume your workouts.

Stay hydrated. It's important to stay hydrated while you're sore to flush the kidneys and prevent protein buildup in the blood, Clarkson said. Watch your urine to make sure it's a light yellow, she said; if your urine turns brown, you're on your way to rhabdomyolysis and need to get to an emergency room.

Work up; cool down. There's little you can do to prevent DOMS. Cooling down helps remove lactic acid that gives you that muscle burn during exercise, and stretching can help prevent a pulled muscle. But neither stretching nor cooling down will do anything to prevent next-day soreness, Clarkson said. Your best bet to mitigate soreness is to gradually build up to strenuous exercise with lighter versions of the activity over several days prior, she said.

Find temporary relief. There's also little you can do to speed recovery from soreness. Massage, ice, stretching, a warm bath or taking anti-inflammatories can make your muscles feel better temporarily, but they won't make them heal faster, Clarkson said. High dosages of antioxidants such as vitamins E, C and beta-carotene might also help, she said.

Be smart. In some cases, what you think is soreness could be injury. See a doctor if:

• You have acute, sharp pain as opposed to the dull burn of soreness.

• The pain is only on one side of your body. (Soreness is usually symmetrical.)

• The pain gets worse during light exercise.