Muscle soreness after a workout: why it happens, training through it and when to worry

Sore muscles a day or two after training are normal, but they raise a lot of questions. Here is why soreness happens, how to train around it and when pain is something more than ordinary soreness.

You started a new program, did walking lunges for the first time in months or added a couple of extra sets, and now the stairs feel like a challenge. Muscle soreness after a workout is something almost everyone who trains has felt. This guide explains in plain terms what it is, why it shows up, whether you can train through it and how to tell normal soreness from pain that might mean an injury.

This is not medical advice. If you are unsure about what you are feeling, or worried about it, talk to a doctor or another qualified health professional.

What is muscle soreness after a workout?

The tenderness and stiffness that show up a while after training, rather than during the session, is usually called delayed onset muscle soreness, or DOMS. It tends to build over several hours, feels worst the next day or the day after, and then gradually fades. The muscle is tender to the touch, stiff when you stretch it and feels weaker when you use it.

Exactly what goes on inside the muscle is not fully understood. A common explanation is that unfamiliar loading puts small amounts of stress on the muscle tissue, and the repair work that follows brings on the soreness. What matters for you is that soreness on its own is a normal response to something new, not a sign that you did something wrong.

It is not lactic acid

You may have heard that soreness comes from lactic acid building up in your muscles. That idea has largely been dropped. Lactate is cleared fairly quickly after exercise, long before soreness peaks, so it does not explain why your legs still ache two days later.

Soreness is not proof of a good session

Plenty of people believe a workout only counts if it hurts the next day. Soreness mostly tells you the load was unfamiliar, not that it was effective. Someone who trains consistently with the same exercises often gets very little soreness and still makes progress. Track progress in your training log instead: more reps, heavier weights, faster times.

Why new exercises and extra volume make you sore

Your body adapts quickly to whatever it does often. That is why soreness typically shows up in these situations:

• New exercises. Switch from back squats to Bulgarian split squats and your muscles are loaded at new angles and lengths, so soreness follows even with light weights.
• More volume. Going from three to five sets, or adding an extra session each week, raises your total workload.
• Coming back after a break. After a holiday, a cold or a few weeks off, even a normal session can leave you very sore.
• Lowering under control. The part of a movement where the muscle brakes a weight, such as lowering the bar in a Romanian deadlift, or running downhill, tends to cause more soreness than the lifting part.
• New formats. A first circuit class packed with jumps and lunges, or a HYROX simulation with sandbag lunges and sled pushes, can make you sore in places you forgot you had.

The good news is that your body gets used to it. Repeat the same exercise within a week or two and the soreness is usually much milder.

Can you work out with sore muscles?

In most cases, yes. Mild to moderate soreness is rarely a reason to skip training altogether. The better question is what to train and how hard.

Rules of thumb for the session

• Train other muscle groups. Legs wrecked from yesterday? Do upper body today. That is one of the perks of a split routine.
• Warm up properly. Soreness often eases once you are warm.
• Reduce the load if your movement is affected. If you cannot squat as deep as usual, for example, use lighter weights or fewer sets rather than grinding through with worse technique.
• Skip max attempts. A day of heavy soreness is not the day to test a new one-rep max.

Severe soreness where you can barely use the muscle is a signal to go easy on that area for a few days.

Running and HYROX

Runners often get sore calves and quads after hill repeats, a long run or a race. An easy run at conversational pace is usually fine, but hold off on intervals and tempo runs until your legs feel normal again. The same goes for HYROX training: pick an easy row or bike session over another round of walking lunges on sore glutes.

What tends to help with sore muscles

Nothing makes soreness disappear instantly, and plenty of products promise more than they deliver. What many people find helpful are the simple things:

• Light movement. A walk, an easy bike ride or some gentle mobility work usually makes stiff muscles feel looser.
• Sleep. Your body recovers while you sleep. Short or restless nights do not make bouncing back any easier.
• Warmth. A hot shower or bath can feel good, even if the effect is mostly that you feel better in the moment.

Many people enjoy stretching, foam rolling and massage. Whether they actually shorten soreness is less certain, so do them if you like them, but do not expect miracles. Do not take painkillers just so you can train hard. If you have questions about medication, ask a pharmacist or your doctor.

Avoid the worst of it with sensible progression

You cannot avoid soreness completely, and you do not need to. But you can avoid the worst version of it:

1. Start light with new exercises. Do two sets instead of four in the first week and leave plenty of reps in the tank.
2. Increase one thing at a time. Weight, sets or number of sessions, not everything at once.
3. Stick with your exercises for a while. Someone who switches programs every week gets more soreness than someone who runs the same plan for several weeks.
4. Log what you do. When you can see last session's numbers, it is easier to add just the right amount.

If you are new to lifting, our guide to a workout plan for beginners shows how to set up your first weeks without overdoing it. In TANK you can log sets, weights and sessions for free, so you can see when you stepped things up and connect that to how your body responds.

Soreness or injury? How to tell the difference

Soreness and injury can sometimes feel similar, but there are some typical differences. Use them as a way to think things through, not as a way to diagnose yourself.

When to get medical advice

Contact a doctor or your local health service if you are unsure or worried, especially if you have:

• severe pain that does not improve after a few days
• obvious swelling, bruising or you cannot put weight on a joint
• pain that started suddenly during your workout
• numbness, tingling or loss of strength
• dark or brown urine after a very hard session, especially together with severe muscle pain and swelling

The last point can be a sign of a rare but serious condition and needs prompt medical attention. In an emergency, call your local emergency number.

The bottom line

Muscle soreness after a workout is a common response when you do something new or more than usual. It says little about how good the session was and usually goes away on its own. You can normally keep training, but switch muscle groups or lower the load. And if the pain feels different, sharp or simply will not go away, get it checked by a professional.