DOMS stands for delayed onset muscle soreness: the ache and stiffness that shows up 12 to 24 hours after a workout and peaks somewhere between 24 and 72 hours. It's caused mainly by unfamiliar movements and eccentric (lowering) muscle work, which create tiny disruptions in the muscle fibers. The soreness fades within a few days as the tissue repairs and adapts.
Why it matters
Because almost everyone reads it wrong. Soreness tracks novelty, not effectiveness. Your first lunge session in months will leave you hobbling for three days. The tenth one? Barely a whisper, even if it built more muscle. That's the repeated bout effect: one exposure to a movement dramatically blunts soreness the next time. So chasing soreness as proof of a good workout pushes people toward random, ever-changing programs, which is exactly what stalls progress. A productive session often leaves you feeling almost nothing the next day.
How to use it in training
Expect DOMS whenever you introduce something new: a new exercise, a big volume jump, extra emphasis on slow lowering. Ease in. Two or three sets the first week beats five sets and a lost weekend.
When you're sore, light movement helps more than the couch does. Easy cardio, walking, gentle sets with the sore muscle. And you can train through mild soreness safely. If a muscle is still very sore after 72 hours, that's your cue to scale back the next dose, not push harder.
Related terms
Go deeper
Want the full science on why soreness happens and what actually helps? Read our breakdown: Delayed onset muscle soreness.