Delayed onset muscle soreness is one of the few training phenomena with a genuinely predictable timeline, and one of the few that consumer wearables are completely blind to. Both facts are worth knowing, especially if you have ever opened an app that told you that you were 100 percent recovered while you were struggling to sit down.
The timeline
Hours 0 to 12. Little or nothing. Any immediate burning during the session is a different mechanism entirely and clears within minutes.
Hours 12 to 24. Onset. Stiffness and tenderness begin, usually noticed getting out of a chair or down stairs.
Hours 24 to 72. Peak. Most people are worst on day two. Strength in the affected muscle is measurably reduced, which is real and not just discomfort.
Days 3 to 5. Resolution for most sessions.
Up to 7 days. Genuinely novel or heavily eccentric work, downhill running, a first session of Nordic curls, a return after months off.
Why your recovery score disagrees with your legs
This is the part worth internalising. A recovery or readiness score is computed from autonomic signals measured overnight: heart rate variability, resting heart rate, respiratory rate, temperature. Those describe how your nervous system and cardiovascular system are coping.
DOMS is a local inflammatory response to microdamage in specific muscle fibres. There is no reason a wrist sensor would detect it, and it does not.
So a green recovery score after leg day is not a bug. It is the app correctly reporting that your autonomic system is fine, while saying nothing at all about your quadriceps, because it cannot. The full argument is in why your wearable has no idea which muscles are tired.
Soreness is a bad proxy for a good session
The strongest determinant of how sore you get is how unfamiliar the movement was, followed by how much eccentric loading it involved. Neither of those tracks the stimulus for hypertrophy or strength particularly well.
The practical consequence: a well-programmed session in an exercise you do every week may leave you barely sore and drive plenty of adaptation, while a novelty circuit you will never repeat wrecks you for three days and builds almost nothing. Using soreness to grade your training will systematically push you toward variety for its own sake.
What to do while it lasts
Train something else. The most useful response. Sore legs do not stop upper body work, and vice versa. This is the entire argument for organising training by muscle group rather than by day of the week.
Move the sore muscles gently. Easy cycling, walking, light sets. Modest but real relief, and it beats complete stillness.
Eat and sleep. Repair is protein synthesis, and protein synthesis needs both. Unremarkable, and the highest-leverage thing on the list.
Do not stretch it away. The evidence for stretching reducing DOMS is close to nil, whether before or after. It is not harmful, it just does not do this job.
To organise training so the sore groups always have something to do, see building a split around muscle recovery.