Hurts so good: for effective workouts, learn to distinguish between productive discomfort and the pain of injury

Muscle & Fitness/Hers, July, 2002 by Amanda E. Vogel

When Monday's killer lunges make your legs feel like lead by Wednesday, have you trained too hard, or are you on your way to a better body? Although some kinds of physical discomfort signal injury, others are natural extensions of growing stronger and fitter -- as long as you don't overdo it. Knowing how to differentiate between appropriate sensations of pain and harmful ones will help you reach greater heights of fitness more efficiently ... and safely.

Is there such a thing as "good pain" during exercise? Not exactly, says Stephen G. Rice, MD, PhD, sports medicine specialist and program director for both the Sports Medicine Fellowship Program and Jersey Shore Sports Medicine Center in Neptune, New Jersey. "It's one thing to feel exhausted or tired, but if it hurts everywhere, that's not what you're looking for," he explains.

The good side of pain

So what should you look for? Exercise physiologists identify two kinds of acceptable discomfort from intense exercise: 1) lactic acid buildup, which occurs during a workout, and 2) a post-exercise sensation called delayed-onset muscle soreness (DOMS).

Lactic acid buildup: This byproduct of anaerobic exercise, such as heavy resistance training and sprinting, creates a burning feeling in the working muscles. "That sensation means the muscle is exhausted -- and that's a good thing," says John Acquaviva, PhD, exercise physiologist, personal trainer and assistant professor of health and human performance at Roanoke college in Salem, Virginia. "Lactic acid buildup is natural and indicates that you're working intensely."

Expect to feel a lactic acid burn as you near the end of a strenuous weight-training set or super-tough indoor cycling drill. The discomfort is temporary; when you stop the activity, the burn also subsides as lactic acid clears from the muscle. And just to set the record straight, "Lactic acid does not damage the muscle or cause prolonged soreness," says Michele Olson, PhD, a professor of exercise science at Auburn University at Montgomery in Alabama.

Delayed-onset muscle soreness (DOMS): Have you ever fired off three or four spirited sets of squats, maybe after a hiatus from the gym due to illness or a holiday, then yelped in agony just trying to make it out of bed a day or two later? That's DOMS.

"Delayed-onset muscle soreness means you took your body to a level it hasn't seen for a while -- or ever," Acquaviva notes. "This is what allows your muscles to grow." Although any exercise you aren't accustomed to can lead to DOMS, Acquaviva points to flyes, lunges and squats as the biggest soreness-causing culprits, partly because they put the affected muscles beyond their normal range of motion. Research suggests that eccentric contractions, or the negative phase in resistance training, may also contribute to this residual soreness.

DOMS is common in people who are new to working out, trying an unfamiliar exercise, revisiting one they haven't tackled lately, or going for greater exercise intensity, duration or frequency. "It can occur from fairly intense aerobic or anaerobic activity and results in microscopic tearing of the actual muscle fibers," explains Acquaviva. "The tears cause the muscle to shorten, creating a sore feeling 24-48 hours [after exercise]." Olson adds that inflammation from the tiny tears is also to blame.

Since DOMS is associated with a desired increase in muscle strength and size, should you worry if you don't feel it all the time? No. "If you work out regularly, your body will adapt and muscle soreness will be at a minimum," states Acquaviva. In fact, experiencing DOMS on most days or to the point where even slight movement causes significant pain may mean you're training too hard, which can lead to an overuse injury down the road.

If you're stiff and sore after every workout, you may be doing other things wrong, as well. For example, consistently skipping out on stretching and/or exercising too infrequently can result in ongoing discomfort.

The bad side of pain

Whoever dreamt up the familiar "no-pain, no-gain" adage must have spent a lot of time in the doctor's office. "The saying 'No pain, no gain,' should really be 'No fatigue, no gain,'" insists Acquaviva, who distinguishes between good and bad pain in muscles according to whether there's microscopic tearing (good) or slight rearing (bad). "This sounds like splitting hairs, but that's really the difference between pain and just fatigue." You want to tire your muscles, not hurt them.

Injuries such as strains, sprains, damage in or around the joints, and inflammation of the tendons or bursae (tendinitis and bursitis, respectively) produce pain that isn't associated with increased fitness. In fact, ignoring these ailments can make the impairment worse, possibly preventing future exercise and ultimately diminishing your existing fitness gains.

Acute pain due to injury: How do you know when pain is due to injury and not just a rigorous workout? Acute pain, sometimes accompanied by swelling, comes on abruptly, during or soon after exercise. Any snapping or popping sound, and shooting and/or gripping pain, that may cause you to stop activity is a loud and clear signal that something's amiss, Olson warns.