Have you ever finished a workout feeling great, only to wake up the next morning struggling to walk down the stairs?
That stiffness and muscle soreness you feel after exercise is known as Delayed Onset Muscle Soreness, or DOMS. It’s one of the most common experiences for anyone who exercises, whether you’re completely new to training or a seasoned gym-goer pushing yourself with a new challenge.
Many people assume soreness means they’ve had a “good workout”, while others worry they’ve injured themselves. In reality, DOMS is simply a normal response to exercise that your body isn’t fully adapted to yet.
So why do we get DOMS after exercise? Here’s what’s actually happening inside your muscles and why soreness develops in the days after training.
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During Exercise: Challenging the Muscle
When we exercise, our muscles are placed under stress, in particular during strength training, running downhill, plyometric exercises, or whenever we perform movements that our body isn’t accustomed to.
As muscles contract repeatedly under load, tiny microscopic disruptions occur within the muscle fibres and surrounding connective tissues. This isn’t a serious injury, but rather a normal part of the training process.
Exercises that involve a lot of eccentric loading, where the muscle is lengthening while producing force, tend to create the most muscle damage. Examples include lowering into a squat, controlling the descent of a deadlift, or running downhill.
This is also why easing into unfamiliar movements matters. Taking a few minutes to prepare the body, like this 10 minute running warm-up, helps your muscles meet the work ahead rather than being caught off guard.
At this stage, you won’t usually feel sore immediately. The processes that create DOMS are only just beginning.
The Inflammatory Response: Why Soreness Appears Later
Following exercise, the body recognises these small areas of muscle damage and begins a natural repair process.
Over the next 24 to 72 hours, inflammatory cells move into the affected tissues. These cells help clear away damaged material and begin rebuilding stronger muscle fibres.
During this process, chemicals are released that increase sensitivity around the muscle. Combined with a small amount of swelling, this creates the familiar feelings of stiffness, tenderness, and soreness associated with DOMS.
This is why soreness doesn’t appear straight after training. It takes time for the inflammatory response to develop, which is why symptoms often peak one or two days later.
Common Symptoms of DOMS include:
- Muscle tenderness when touched
- Stiffness when moving
- Reduced range of motion
- Temporary loss of strength
- Discomfort during activities such as walking downstairs, sitting down, or standing up
While these symptoms can be uncomfortable, they are usually temporary and improve as the muscle recovers.
How Long Does DOMS Last?
For most people, DOMS sets in around 12 to 24 hours after a session, peaks somewhere between 24 and 72 hours, then gradually eases over the following days. If you’ve done something very unfamiliar, it can linger a little longer, but it should steadily improve rather than get worse.
Recovery Phase: Adapting and Getting Stronger
The purpose of this repair process is adaptation.
As the body repairs the microscopic damage caused by training, muscles become stronger and more resilient. This is one of the key mechanisms behind improvements in strength, fitness, and physical performance.
Supporting that repair process with the basics matters too. Sleep, hydration and sensible training loads all play a part, which I cover in more detail in Recovery: Are You Getting It Right? and Daily Habits for Better Movement and Faster Recovery.
Interestingly, the more often you perform a particular exercise, the less soreness you tend to experience. This is known as the repeated bout effect. The body learns how to tolerate the stress, making future sessions feel easier to recover from.
This is why your first leg day in months might leave you struggling for days, while a regular training programme eventually produces very little soreness at all.
Should You Train When You’re Sore?
In most cases, mild to moderate DOMS is completely safe to train through.
Light movement, walking, mobility work, or lower-intensity exercise can often help reduce feelings of stiffness and improve blood flow to the muscles. On sore days, something gentle like a morning yoga flow or a hip mobility and strength session can keep you moving without overloading muscles that are still repairing.
However, if soreness is severe enough to significantly alter your movement patterns or affect exercise technique, it may be sensible to reduce training intensity until symptoms settle.
The goal isn’t to avoid soreness completely, but to manage training loads appropriately so your body can recover and continue adapting. If you’d like some practical ways to ease it, I’ve put together a separate guide on how to reduce DOMS.
In Summary
DOMS isn’t caused by lactic acid build-up, and it doesn’t necessarily indicate injury. Instead, it’s a normal response to unfamiliar or challenging exercise that creates small amounts of muscle damage.
The soreness you feel is simply your body’s repair system getting to work.
While it can make everyday tasks feel surprisingly difficult for a day or two, DOMS is usually a sign that your muscles are adapting to a new challenge. With consistent training, appropriate recovery, and gradual progression, those sore post-workout days become far less common.
Disclaimer:
This article is for general information and education only. It isn’t medical advice and shouldn’t replace guidance from a qualified healthcare professional. If your soreness is severe, doesn’t ease within a few days, or is paired with significant swelling, sharp pain, or restricted movement, speak to a GP or physiotherapist.