DOMS: why you're sore, whether it means anything, and training through it

DOMS, or delayed onset muscle soreness, is the stiff, tender, can't-sit-on-the-toilet feeling that arrives a day or two after a session your muscles weren't ready for. It's normal. It mostly means you did something new, something eccentric, or more of something than usual. It does not mean the session was good, and its absence doesn't mean the session was wasted.

Below: what is DOMS, why it happens, the types of soreness worth telling apart, whether DOMS is a sign of muscle growth, and how to train through it without making the week worse. Plan it by hand, or let exrsz, the AI coach space the hard sessions for you.

One rule first: this is about normal training soreness. Sharp pain, pain in a joint, or anything that feels like an injury is a different conversation, and it's one for a professional.

What is DOMS?

DOMS is muscle soreness that builds after exercise rather than during it. A review of the condition describes it as a mild type of ultrastructural muscle injury, caused by eccentric or unfamiliar exercise, with symptoms that typically peak 48 to 72 hours after the session (Hotfiel et al., 2018). That's why the day after leg day is bad and the day after that is worse.

The usual signs, from the same review: reduced strength, stiffness, painful range of motion, and sometimes a bit of swelling. If you've ever walked downstairs sideways on a Wednesday, you've met all of them.

It shows up most when training changes. Another review noted DOMS is most common at the start of a season, when athletes return from a period of reduced activity, and whenever they're introduced to new types of exercise (Cheung et al., 2003). Translation: the first week back, the new program, the first hill session. It's also why a training week built as one plan, like a plan that combines both running and lifting, introduces new stuff gradually instead of all on the same Monday.

It isn't lactic acid

Lactic acid gets the blame in every gym. It's one of several old hypotheses for DOMS, alongside muscle spasm, connective tissue damage, muscle damage, inflammation and enzyme efflux, and the authors of one review concluded that a combination of theories likely explains it (Cheung et al., 2003). More recent work considers damage to the muscle's microstructure, followed by a local inflammatory response, the primary mechanism (Hotfiel et al., 2018).

What causes DOMS

Three things, mostly:

• ›Eccentric work. The lowering half of a movement, where the muscle lengthens under load. Lowering into a squat, the descent of a Romanian deadlift, running downhill. Eccentric activities cause micro-injury more often and more severely than other muscle actions (Cheung et al., 2003).
• ›Novelty. A new exercise, a new range of motion, a new sport. Your body is bad at things it hasn't practiced.
• ›A sudden jump in volume or intensity. Twice the usual sets, or a long run that's suddenly much longer.

That's the reason the best fix for DOMS is boring: introduce new things gradually. The same review recommends bringing in eccentric exercises or novel activities progressively over one to two weeks at the start of, or during, a season (Cheung et al., 2003).

The repeated bout effect

Do the same brutal session again a week or two later and you'll be far less sore. That's the repeated bout effect: a repeat of similar eccentric exercise causes less damage than the first time (McHugh et al., 1999). The mechanism isn't settled; the review lists neural, connective tissue and cellular explanations, probably working together.

The practical upshot: soreness fades as a program becomes familiar, even if you're working just as hard. Which leads to the question everyone actually wants answered.

Is DOMS a sign of muscle growth?

No, not reliably. Soreness tells you the session was unfamiliar. It doesn't tell you it was effective.

The best direct evidence comes from a study that took muscle biopsies from ten young men over ten weeks of resistance training (Damas et al., 2016). In the first week, muscle damage was highest and muscle protein synthesis was elevated, but neither was related to the eventual muscle growth. By weeks three and ten, damage had dropped off, and that's when protein synthesis started correlating with hypertrophy. The authors concluded that growth comes from accumulated increases in protein synthesis after the muscle damage has faded.

Read that again. The phase where you were most sore was the phase where the muscle-building response wasn't going toward growth yet. It was busy with repairs.

So chasing soreness is chasing the wrong signal. A program that leaves you crippled every session is mostly a program that keeps changing, or one that's too hard to recover from. Real progress looks like smart progression: the same lifts, slightly heavier or slightly more reps, week after week, with soreness becoming rarer as you adapt.

The reverse is also true. No DOMS doesn't mean no progress. If your lifts are going up and your runs are getting easier, the soreness has done its job by disappearing.

Types of DOMS (and the soreness that isn't DOMS)

There's no official list of types of DOMS. But there are a few kinds of soreness worth telling apart, because they call for different responses:

The timing of classic DOMS follows the 48–72 hour peak described in the review above (Hotfiel et al., 2018). The rest is coaching practice: DOMS is dull, spread across a muscle, on both sides if you trained both sides, and eases a little once you warm up. Injury pain tends to be sharp, specific, and indifferent to your warm-up.

One more: if soreness is extreme, comes with a lot of swelling, or your urine turns dark after a brutal session, that's a see-a-doctor-today situation, not a foam-rolling one.

Should you train with DOMS?

Usually yes, with some adjustments. The question is not "am I sore" but "can I do this session with good form, at the planned effort, without the soreness changing how I move".

What the research suggests: exercise is the most effective way to relieve the pain of DOMS, but the relief is temporary, and athletes who must train daily should reduce the intensity and duration of exercise for one to two days after a session that caused heavy DOMS, or train less affected body parts instead (Cheung et al., 2003). The same review noted DOMS can reduce range of motion and peak torque, which is why heavy, technical work on very sore muscles is a bad bet.

A simple rule set:

• ›Mild DOMS: train as planned. It'll probably ease during the warm-up.
• ›Moderate DOMS: keep the session, lower the load or volume on the sore muscles, or swap the order of the week so they get another day.
• ›Heavy DOMS: train something else. Upper body after a leg-wrecking day. Easy movement, not intensity.

Light movement on sore days is where active recovery earns its name: a walk, an easy spin, gentle mobility. Easy enough that it feels like nothing.

Running with DOMS

Easy running on sore legs is usually fine and often feels better after the first ten minutes. Intervals on sore legs are a worse idea, because the session's whole point is quality and sore muscles don't produce it. Flat routes beat hills, since downhill running is exactly the eccentric load that caused the problem.

The general rule: sore legs get running slow on purpose, not a tempo they'll do badly.

Lifting with DOMS

Sore from running? Lifting upper body is fine. Lower body can still happen at lighter loads, but don't test a max on quads that can barely get you off the couch. Sore from lifting? An easy run is fine. A hard run the day after heavy squats is the classic hybrid mistake, which is why what to do first: run or lift matters as much as which days you train.

How to keep DOMS from wrecking your week

You can't avoid soreness entirely, and you don't need to. You can stop it from running your schedule.

• ›Ramp new things in. New program, new exercise, new hill route: start with fewer sets and shorter sessions for the first week or two.
• ›Progress in small steps. Most of the time, bad DOMS means a big jump. Smaller jumps, less soreness, same direction.
• ›Plan the week around it. The day after a big eccentric session isn't the day for intervals.
• ›Don't change programs every month. Constant novelty means constant soreness and little to show for it. Stable programs inside a guide to periodization let your body adapt and the soreness fade.
• ›Take the lighter weeks. Soreness that never fully clears across weeks is a load problem, and scheduled deloading is the fix for load problems.

What about recovery tools?

People throw a lot at DOMS. A meta-analysis of 99 studies found active recovery, massage, compression garments, water immersion, contrast water therapy and cryotherapy all reduced DOMS to some degree, with massage the most effective (Dupuy et al., 2018). An older review found several of those methods had no effect, so the picture is mixed (Cheung et al., 2003). None of them replace the boring basics: sensible progression, sleep, enough food, and time.

When soreness is a warning sign

DOMS that clears in a few days is training doing its job. Soreness that never clears, sessions that keep getting harder at the same effort, and fatigue that doesn't lift with rest are something else. That pattern belongs in the conversation about recovering from overtraining, not muscle soreness. And pain that's sharp, localized or getting worse needs a professional, not another rest day.

How exrsz handles this

exrsz builds a periodized plan from your goal, schedule, level and equipment, and balances running and lifting in one week so heavy leg days and hard runs don't land back to back. It adapts each week to how you actually trained and reshuffles missed sessions instead of piling them on top of sore legs.

FAQ

What is DOMS?

DOMS (delayed onset muscle soreness) is soreness that develops in the hours and days after unfamiliar or eccentric exercise, typically peaking 48 to 72 hours later (Hotfiel et al., 2018). It's a normal response to new or harder training and usually clears within a few days.

Is DOMS a sign of muscle growth?

Not reliably. In a biopsy study, the muscle-building response early in training, when damage was highest, wasn't related to growth; it was later, once damage had faded, that it tracked hypertrophy (Damas et al., 2016). Progress in your lifts is a better signal than soreness.

What are the types of DOMS?

There's no official classification, but it helps to separate acute soreness during or right after a session, classic DOMS that peaks a day or three later, and pain that isn't DOMS at all: sharp, localized or in a joint. That last one needs a professional.

Should I work out with DOMS?

Usually yes, but adjust. Mild soreness is fine to train through; with heavy soreness, cut intensity for a day or two or train other body parts, as one review recommends (Cheung et al., 2003).

Why am I less sore when I repeat a workout?

That's the repeated bout effect: repeating similar eccentric exercise causes less muscle damage than the first time (McHugh et al., 1999). It's why soreness fades once a program becomes familiar.