Why Do Muscles Hurt the Day After Exercise? Understanding DOMS
You finish a workout feeling pretty good. Maybe you tried a few new exercises, added more weight than usual, went for a long hike, or simply pushed yourself a little harder than normal.
Then the next morning arrives.
Your legs feel stiff. Your shoulders are sore. Going down the stairs suddenly feels like a workout of its own.
That delayed soreness is very common, and it has a name: Delayed-Onset Muscle Soreness, or DOMS.
Why does muscle soreness show up later?
DOMS is different from the burning or fatigue you might feel while exercising.
It usually starts several hours after an unfamiliar or challenging activity, often becoming noticeable the next day. For many people, soreness feels strongest somewhere between 24 and 72 hours after exercise before gradually improving.
You may notice that the muscles feel tender, stiff, weaker than usual, or simply uncomfortable when you move.
This is especially common when you do something your body is not used to.
Maybe you haven't done squats in months. Maybe you suddenly walked 20 kilometres on vacation. Or perhaps you started a new exercise program and increased the intensity too quickly.
Your body is simply responding to a new type of physical demand.
Some exercises are more likely to cause soreness
Certain movements are particularly good at producing DOMS.
One example is eccentric exercise, which happens when a muscle is producing force while lengthening.
Think about slowly lowering a dumbbell during a biceps curl, walking downhill, lowering yourself into a squat, or controlling your body as you walk downstairs.
These types of movements can create more post-exercise soreness, especially when your body is not accustomed to them.
The biology behind DOMS is actually quite complicated. It involves changes in and around the muscle, inflammation-related processes, and the way your nervous system responds to the exercise.
That is why saying that soreness is simply caused by “tiny tears in the muscle” is an oversimplification.
What about lactic acid?
You may have heard someone say:
“Your muscles hurt because of lactic acid.”
It is one of the most persistent exercise myths.
The metabolic changes that happen during exercise disappear much too quickly to explain why your thighs can still feel sore two days after a workout.
So if you wake up aching after leg day, it is not because lactic acid has been sitting inside your muscles overnight.
DOMS develops through different processes.
Does soreness mean you had a better workout?
Not necessarily.
This is another common misconception.
You can have an excellent workout without feeling sore afterward.
In fact, as your body becomes more familiar with an exercise, you will often experience less soreness even when you continue training effectively.
For example, your first session of lunges might leave you walking strangely for two days. After several weeks of doing them regularly, the same exercise may cause little or no soreness.
That does not mean the exercise has stopped working. Your body has simply adapted.
So you do not need to chase soreness to make progress.
Should you stretch sore muscles?
If gentle stretching feels good, there is usually nothing wrong with doing it.
But stretching is not a magic cure for DOMS.
Research has not shown that stretching after exercise reliably prevents or eliminates next-day muscle soreness.
That does not make stretching useless. It can still improve flexibility and feel relaxing.
The important thing is not to assume that a sore muscle needs to be aggressively stretched.
Sometimes your body simply needs time.
What can you do when you're sore?
You usually do not need to spend the whole day lying on the couch.
Gentle movement often feels better than staying completely still.
An easy walk, light activity, reducing the intensity of your next workout, and allowing heavily worked muscles some recovery time can all be reasonable approaches.
Sleep also matters. Poor sleep can increase sensitivity to pain, which may make already-sore muscles feel even less comfortable.
And if you are starting a new exercise program, one of the simplest ways to reduce excessive soreness is to increase the workload gradually rather than doing too much too soon.
Massage therapy may also help some people feel less sore after exercise. Research suggests it can modestly reduce the sensation of DOMS, although that does not mean massage instantly repairs the muscle or dramatically speeds up the biological recovery process.
When should you be more careful?
Normal post-exercise soreness should gradually improve.
Very severe pain, major swelling, significant weakness, or symptoms that continue getting worse should not simply be assumed to be DOMS.
One particularly important warning sign is very dark, tea- or cola-coloured urine combined with severe muscle pain or weakness. Those symptoms require prompt medical attention.
Fortunately, this is very different from the ordinary stiffness most people experience after a challenging workout.
So, should you worry about being sore?
Usually, no.
Feeling sore after trying something new or increasing your activity is common.
But remember that soreness is not a measurement of how effective your workout was.
Your muscles do not need to hurt for exercise to be beneficial.
If you are sore, give your body a little time, keep moving comfortably, recover well, and gradually build up your activity.
Your body is very good at adapting — and chances are, the same workout that leaves you sore today will feel much easier a few weeks from now.
This article is for educational purposes only and is not a substitute for individualized medical advice, diagnosis, or treatment.
