As the warm weather brings people outdoors to exercise after months of lethargy, the accompanying muscle soreness can send them back to cozying up on the couch.Fred Lum/The Globe and Mail
All across the country, people are rolling bikes out of their sheds and digging tennis racquets out of their closets. Then, a day or two later, they're hobbling around with aching muscles and shooting pains, cursing the return of spring.
This "delayed onset muscle soreness," or DOMS, is the body's default response to unaccustomed exercise. To soothe or prevent it, some swear by gruelling ice baths, some by compression socks or massage and others by a lengthy list of dubious lotions and pills. But the most powerful remedy, according to Dr. Pascal Madeleine, is somewhat unexpected.
"The best one is, to me, exercise," says Madeleine, head of the Physical Activity and Human Performance Group at Aalborg University in Denmark, who studies the mechanisms underlying muscle soreness.
Madeleine's advice relies on a poorly understood phenomenon called the "repeated bout effect." While it might seem obvious that you'll get less sore after doing a workout for the second time, the protection offered by the repeated bout effect kicks in after a single session and lasts for weeks, even if you don't do enough to get really sore the first time. And, more puzzlingly, a workout with one arm or leg will also protect the opposite limb from subsequent soreness. Scientists still aren't sure how this works, but as you prepare to return to warm-weather activities, it's worth figuring out how to harness it.
The underlying cause of DOMS is microscopic damage to your muscle fibres, particularly from "eccentric" muscle contractions when your muscle is lengthening as you try to shorten it. Lunges and downhill running are two common examples. This damage triggers a complex sequence of muscle repair processes, resulting in inflammation and the release of noxious substances that make your nerve endings more sensitive – and that's where the pain comes from.
How, then, does damaging your muscles once make them less susceptible to damage the next time? Part of the answer lies in the muscle cells themselves. The initial workout weeds out the weakest fibres, and the other fibres adapt and repair themselves to be stiffer and more resistant to damage.
This isn't the whole story, though, since it can't explain why one-armed exercise confers DOMS protection on both arms, notes Dr. Dean Burt, a researcher at Staffordshire University in Britain. One possibility is that after one painful episode, the nervous system adjusts to recruit more slow-twitch fibres, which are less susceptible to damage, instead of fast-twitch fibres.
Madeleine and his colleagues offered another possibility in a 2013 study published in the European Journal of Applied Physiology. They had subjects do two DOMS-inducing workouts a week apart, then used two different techniques to measure their pain the next day.
The first technique used an algometer, essentially a blunt needle that applies mounting pressure until the subject says it hurts. As expected, pain sensitivity in the exercised muscle was higher the day after the first workout, but – thanks to the repeated bout effect – didn't increase the day after the second workout.
But does this change take place only in the affected muscle, or in the entire nervous system? To find out, the researchers applied steadily increasing jolts of electricity to their subjects' feet to assess the "nociceptive withdrawal reflex," which is the automatic reflex-driven response that causes you to yank your finger off a hot stove before you've even registered that it's burning. Once again, the reflex was easier to trigger (meaning the whole body was hypersensitive to pain) the day after the first workout, but unaffected after the second workout.
The takeaway message from all this is that avoiding soreness isn't just a matter of getting fitter, which takes weeks or months. You can dramatically change your susceptibility to soreness with just a single bout of exercise – and it doesn't have to be extreme.
Burt and his colleagues published a study in February, also in the European Journal of Applied Physiology, in which they compared the effects of either five or 10 sets of 10 squats. Subjects who did the harder workout were more sore the next day, but when both groups did the harder workout two weeks later, they all experienced the same protection from the repeated bout effect.
In the end, this advice starts to sound suspiciously like plain old common sense: Ease into your routine, build up gradually and so on. Most of us are too impatient to follow these rules, but this research presents a more modest proposal – just hold back for that first workout, and you'll be ahead of the game.
Alex Hutchinson blogs about exercise research at sweatscience.runnersworld.com. His latest book is Which Comes First, Cardio or Weights?
The Lactic Acid Method
One thing that has nothing to do with delayed onset muscle soreness, it's worth noting, is lactic acid (or its constituent molecule, lactate). "Studies have shown that eliciting higher levels of lactate during exercise has no bearing on DOMS," says researcher Dean Burt.
That means that while cooling down or stretching after a workout to flush away lactate may have other benefits it doesn't affect how sore you'll be the next day. Once the muscle is damaged, you can't undamage it. Indeed, a 2012 study by Norwegian researchers found that warming up with gentle cycling before a demanding workout reduced next-day soreness, but doing the same gentle cycling after the workout didn't help.