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Why we get sore after exercise and what to do about it

A few weeks ago, I decided to get back into exercise after taking some time off over the summer.

I did my workout, and I was feeling great. But the next day my legs were so stiff and sore I could barely walk.

The cause is something scientists call "delayed onset muscle soreness" — or DOMS for short.

If you've experienced it, you might be wondering why it happens and whether you can avoid it. We spoke to two exercise scientists to find out.

Only some exercises make you sore

Professor Ken Nosaka from Edith Cowan University has spent years researching DOMS.

He says unlike pain associated with lactic acid, which is metabolised during and soon after exercise, DOMS is generally felt between 12 and 24 hours after a workout.

And while scientists have a range of theories, it's not exactly clear what causes DOMS.

What they do know is that the soreness is usually caused by exercises that lengthen the muscles, which are known as “eccentric exercises”.

Eccentric exercises can include things like walking down stairs, lowering a weight slowly or running downhill.

"If you don't do eccentric contractions, you don't get sore at all. For example, when you are doing squats, you are lowering your body. That's very eccentric. But when you are standing up, that's concentric.

"If you just did that concentric phase [standing up], you won't get sore at all."

Keep in mind that if you're experiencing DOMS, you'll only feel the soreness when you're using the muscle — not if you're resting on the couch.

If you're still feeling sore during rest, you may have injured yourself.

Another sign of injury as opposed to DOMS is if the pain doesn't go away within a few days, says Dr Jonathan Peake, a senior lecturer in biomedical sciences at QUT.

You're more likely to get DOMS if you haven't exercised in a while

If you've experienced DOMS yourself, you might have noticed that your body quickly adapts.

A few days after my bout of DOMS, I did another workout with similar exercises. The next day, I felt much better than I had the first time around.

It's due to what's called the "repeated bout effect", Dr Nosaka says.

And it turns out just one workout can protect against a repeat case of DOMS for weeks.

"We find that repeating bout affect can last from four to eight weeks," Dr Nosaka says.

Surprisingly scientists like Dr Nosaka still don't know exactly why this happens.

"I wish I knew the exact mechanism," he says. "That's the million-dollar question."

Does it mean you are overdoing it?

Not necessarily. For Dr Peake, mild muscle soreness that goes away within a few days isn't a bad thing.

"It's an indication that you've worked your muscle, and perhaps there is some muscle breakdown occurring. And we need that muscle breakdown to stimulate muscle growth," he says.

If you are completely stiff and sore like I was, you won't be able to do an intense workout. But if your symptoms are mild, there's likely no harm in continuing to train.

"Unless you experience severe discomfort, and you can't walk or lift your arms, then there's no reason why you should be stopping," Dr Peake says.

"But if it's severe, avoiding exercise for two or three days is advised. You can get back into your program after that."

All that said, you can mostly avoid DOMS by gradually working up the intensity of your exercise. It's an approach that Dr Nosaka recommends, as it takes advantage of the repeating bout effect.

"Some people believe that if you don't feel any muscle pain, there's no gain. But that is not correct," he says.

"I think no pain means more gain."

The best way to recover

Exercise scientists have looked at all sorts of recovery techniques for DOMS, from massage to ice baths.

And while there is some evidence that these approaches can provide temporary relief, they don't seem to speed up recovery time.

"The objective evidence … doesn't seem to show a lot of benefits to post-exercise interventions," says Dr Peake.

"Time is a key factor. And generally healthy young people should recover in four days. Older people don't recover quite as quickly."

There may be health benefits to 'eccentric' exercises

While these eccentric exercises can lead to DOMS, it doesn't mean you should avoid them.

In fact, Dr Nosaka spends a lot of time trying to encourage people to do more of them. There's a simple reason: they seem to be good for health.

In one research project, Dr Nosaka and colleagues compared a group of people who only walked down a set of stairs (an eccentric exercise) to a group who only walked up the stairs (a concentric exercise).

They found that the eccentric exercises seemed to be more effective in improving muscle function, physical fitness, balance, bone density, blood pressure and other measures of health.

It also seems eccentric exercises may even have benefits for brain function.

Many well-known exercises like lunges, squats and deadlifts involve eccentric movements. Dr Nosaka also made a video demonstrating some basic exercises you can do at home with a chair.

Article from ABC Everyday

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