Delayed onset muscle soreness, or DOMS, is muscle pain that sets in one to three days after intense exercise — hence "delayed," as opposed to the burning fatigue you feel during a set. According to the Cleveland Clinic, DOMS typically shows up after trying a new activity, a new type of training, or a workout more intense than what your body is used to.
What's actually happening in the muscle
High-intensity or unfamiliar exercise — especially movements with a heavy eccentric (lengthening) component, like the lowering phase of a squat — causes tiny, microscopic tears in muscle fibers. Cleveland Clinic explains that the body responds to this micro-damage with increased inflammation, and that inflammatory response is what produces the delayed soreness. In other words, DOMS is generally a sign your body is in the process of repairing and rebuilding muscle fibers, not damage in the injury sense.
Is soreness a good sign?
Not necessarily — and it's not required for progress. DOMS tends to be worst when you introduce a new exercise, a new training split, or a jump in volume, and it fades as your body adapts to that specific stimulus over a few weeks. Experienced lifters doing familiar programming often feel little soreness even while still making progress via progressive overload. Chasing soreness as a workout goal usually just means constantly switching exercises before you've adapted to any of them — which works against consistent progress.
When soreness is a warning sign instead
Cleveland Clinic notes that DOMS can usually be managed at home with rest, light movement, and time, but recommends talking to a healthcare provider if soreness is frequent, severe, or doesn't improve — since that pattern can point to inadequate recovery or an actual injury rather than normal training adaptation. Sharp, localized pain (as opposed to a dull, whole-muscle ache), swelling, or soreness that worsens rather than fades over several days are reasons to get it checked out rather than push through it.
The takeaway
Some soreness after a new or harder-than-usual session is normal and reflects your muscles adapting. It isn't a requirement for a workout to "count," and it isn't something to chase every session. Give sore muscles time, prioritize sleep and protein to support repair, and treat unusually severe or persistent pain as a signal to dial back rather than push through.