Why do my muscles ache two days after a workout?

Muscle soreness that arrives a day or two after exercise has a name - DOMS, delayed-onset muscle soreness - and a timeline: it starts 12 to 24 hours after the workout, peaks around 24 to 72 hours, and fades within a week. The cause is microscopic damage to muscle fibers from unaccustomed work, especially eccentric exercise - the lowering phase, like descending squats, downhill running, or lowering weights. It is the adaptation process, not an injury: the muscle rebuilds stronger, which is why the same workout hurts far less the second time. What helps: light movement - walking, easy cycling - beats total rest for blood flow; gentle stretching, hydration, sleep, and normal protein intake support repair. Ice baths and fancy recovery tools show modest effects at best. The real prevention is progression - increase training load gradually, and expect soreness with anything new. MedlinePlus notes muscle aches from overuse are the most common kind and resolve on their own. The line between DOMS and injury: DOMS is diffuse, symmetrical-ish, and improves daily; a strain or tear is sharp, localized, sometimes with swelling or bruising, and hurts with use from the moment it happened. Pain that stops you from using the limb, or soreness with dark urine - rare but dangerous rhabdomyolysis after extreme exertion - needs a doctor promptly. Pymander is a free AI doctor, 24/7 by text. Describe the ache and the workout, and it can help you tell sore from injured.