Why Your Muscles Ache a Day or Two After a Workout

The workout itself felt fine. The next morning you were a little stiff, and by the second morning, going downstairs needed a hand on the rail and sitting down on a low chair took some planning. If you’ve just started a new class, gone back to the gym after a long break or spent a Saturday walking down a mountain, you’ll know the feeling.

This is delayed onset muscle soreness, usually shortened to DOMS. It can be alarming the first time, but in most cases it means nothing worse than that your muscles did something they weren’t used to. It also says less about whether the workout was any good than many people assume.

What’s Behind the Ache

DOMS follows exercise you aren’t used to, and especially eccentric work, where a muscle lengthens while it’s under load. Lowering into a squat, the way down in a press-up and walking downhill are all eccentric. A 2003 review described the usual course: soreness builds over the first day, peaks somewhere between 24 and 72 hours after the session, and is gone within five to seven days.

Cheung, K., Hume, P.A. & Maxwell, L. (2003). “Delayed onset muscle soreness: treatment strategies and performance factors.” Sports Medicine, 33(2), 145-164.

Several things go on at once. Small amounts of damage in the muscle fibres set off an inflammatory response, and nerve endings in and around the muscle become more sensitive, so ordinary movement registers as pain. You’re often a bit weaker and stiffer for a few days as well. Lactic acid, the usual suspect, has nothing to do with it. Your body clears it within about an hour of finishing, long before the soreness starts.

Why the Second Week Hurts Less

The first session of a new programme is almost always the worst. One bout of eccentric exercise protects the muscle against damage and soreness from a similar bout for weeks afterwards, which researchers call the repeated bout effect. In practice, the routine that left you sore for days in week one often barely registers by week two or three.

McHugh, M.P. (2003). “Recent advances in the understanding of the repeated bout effect: the protective effect against muscle damage from a single bout of eccentric exercise.” Scandinavian Journal of Medicine & Science in Sports, 13(2), 88-97.

For the same reason, soreness is a poor way to judge a workout. It mostly reflects how new an exercise is to you, and much less how much good it did. Swap in different exercises and you’ll be sore again even after an easier session; repeat a hard session you know well and you may feel almost nothing the next day. Chasing soreness tends to mean changing your routine all the time or doing more than you can recover from, when strength comes from repeating similar training and adding a little at a time.

What Helps, and by How Much

A 2018 meta-analysis compared the common recovery techniques. Massage had the largest effect on soreness and on how tired people felt. Compression garments and cold treatments helped somewhat. Active recovery, such as an easy spin on a bike, did little or nothing for soreness, and neither did stretching.

Dupuy, O., Douzi, W., Theurot, D., Bosquet, L. & Dugué, B. (2018). “An Evidence-Based Approach for Choosing Post-exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation: A Systematic Review With Meta-Analysis.” Frontiers in Physiology, 9, 403.

Stretching also has its own Cochrane review. Across the trials it pooled, stretching before or after exercise reduced soreness by about 1–4 points on a 100-point scale, far too little for anyone to notice. Stretch if you like how it feels or you’re working on flexibility, but don’t expect it to fix the stairs.

Herbert, R.D., de Noronha, M. & Kamper, S.J. (2011). “Stretching to prevent or reduce muscle soreness after exercise.” Cochrane Database of Systematic Reviews, (7), CD004577.

The bigger lever comes before the soreness. Start a new kind of training with less than you think you can manage and build up over a couple of weeks, so each session is only a small step beyond the last. Training while you’re mildly sore is generally fine. Strength is often down for a few days, though, so a hard session on very sore legs is likely to feel worse and go less well.

When It’s Something Else

Ordinary DOMS is a dull, spread-out ache that’s worse when you move or press on the muscle, and it eases a little each day. A few signs point elsewhere. Very dark urine (the colour of cola), severe swelling, real weakness or pain far out of proportion to the workout can be signs of rhabdomyolysis, where damaged muscle releases its contents into the blood and strains the kidneys. It’s rare, and it needs medical help the same day. Sharp pain in a joint, or pain that started suddenly during one particular movement, is more likely an injury than DOMS, and so is soreness that hasn’t eased after a week.

If you’re new to training, Lamplit’s free Foundations plan is a sensible place to begin. It’s four weeks of short bodyweight sessions (two full-body strength days, a core day and a mobility flow each week, roughly 7–20 minutes each), and it starts at a dose built for beginners to recover from. A guided runner counts your reps and rests, and a free Fitness Check sets your level. Whatever training you do, log each session with its intensity, and when you log the next one, add a line to the notes about how sore the last one left you. Repeat a workout a week or two later and you can watch the repeated bout effect in your own notes.

Log your last workout in Lamplit and note how sore it left you. It’s free.