Muscle soreness: where it comes from and what to do about it

Updated: October 9, 2026

You're walking down stairs backwards, sitting on the toilet has become a full-contact sport, and lifting your arms to brush your hair makes you wince. Welcome to the wonderful world of muscle soreness. Don't worry: this is totally normal, it doesn't mean your workout was "effective" or "ineffective," and there are real ways to ease it. Let's bust the myths and give you the actual game plan.

What exactly is muscle soreness?

The technical name is DOMS (Delayed Onset Muscle Soreness). It typically shows up between 12 and 24 hours after exercise, peaks between 24 and 72 hours, then fades within 3 to 5 days.

It is NOT lactic acid. This myth just won't die, but it's flat-out wrong: lactic acid clears from your system within one to two hours after exercise, not two days later. If you're sore the day after tomorrow, lactic acid has nothing to do with it.

Where does it actually come from?

Muscle soreness comes from tiny micro-tears in the muscle fibers and the connective tissue surrounding them. Your body then responds with a small, localized inflammatory response, which triggers that stiff, achy feeling. Three situations tend to cause these micro-tears more than others:

Eccentric contractions: when a muscle lengthens under tension (think the lowering phase of a squat, or the negative on a curl). This is where muscle damage is most significant.
Novelty: a movement, muscle, or range of motion your body isn't used to. That's why a simple hike can leave you sore if you never hike, while a regular runner barely feels a thing.
Unusual volume or intensity: more sets, more weight, more reps than your body is used to handling.

So it's not really about "working the muscle properly" or having a session that "paid off." Plenty of people make huge progress without much soreness at all, and vice versa. DOMS mainly reflects the gap between what you just did and what your body is used to, not the quality of your training.

Don't panic: what soreness is NOT

It doesn't mean you "properly destroyed" your muscles so they can rebuild stronger — muscle growth doesn't require pain.
It's not a marker of progress. After a few weeks of consistent training, you'll get less and less sore for the same workout, even as you keep improving.
It shouldn't be confused with real joint or tendon pain, or an acute injury (sharp, localized pain that shows up during the effort itself).

What to do while you're sore

Light movement, your best friend

Contrary to what you'd think, staying completely still doesn't help. Light activity (walking, easy cycling, gentle mobility work) boosts local blood flow and slightly eases that stiff feeling. Aim for 15 to 20 minutes of low-intensity movement on the days you're sore.

Heat beats cold

Ice baths have long been hyped as the miracle fix. In reality, their effect on perceived pain is only modest, and they may hold back muscle adaptations if you're trying to build muscle (cold may blunt the inflammation your body needs to repair itself). A hot shower or warm bath, on the other hand, relaxes muscles and can bring relief without those downsides.

Massage and self-massage

A light massage or 10 minutes with a foam roller can noticeably reduce how sore you feel, even if the actual effect on tissue recovery is fairly minor. Still, it's a solid comfort tool.

Sleep and nutrition, the real game-changers

Sleep: it's a key window for tissue repair, especially deep sleep. Aiming for 7 to 9 hours a night supports your recovery.
Protein: 1.6 to 2.2 grams per kilo of body weight per day to support muscle repair. Chronic low protein intake clearly slows down recovery.
Hydration: dehydration makes muscle fatigue feel worse. Aim for roughly 30 to 35 ml of water per kilo of body weight per day, more if it's hot out or you're sweating a lot.

What doesn't really have proven benefits

High-dose antioxidant supplements (vitamin C, E): they can actually blunt long-term muscle adaptations.
Long static stretches before or after exercise: they don't meaningfully prevent soreness.
"Pain relief" creams in general: mostly a placebo effect and local comfort, not faster repair.

How to reduce soreness next time

The best method is gradual progression. Your body adapts to a repeated stimulus: the more consistent you are, the less severe your soreness will be, even as you gradually increase the load. In practice:

Bump up your training volume by 10 to 20% max per week when you're getting back into it or switching programs.
Ease into new movements (especially ones with a big eccentric component, like Bulgarian split squats or Nordic curls) gradually, instead of going full intensity from day one.
Do a real, targeted 5-to-10-minute warm-up that preps the specific muscles you're about to train, not just 5 minutes of generic cardio.

In Kaizmax, that gradual approach comes down to simple rules. Your program sets the number of sets and the rep range based on the level you declare in the questionnaire, using exercises suited to that level. And with Premium, the weight suggested during your workout follows the reps you logged last time: it only goes up (+2.5 kg / 5 lb, or +5 kg / 10 lb on most lower-body moves) once you've hit the top of the range on every set, stays the same otherwise, and drops by 10% if a set fell below the bottom of the range. The first time you do an exercise, the suggested starting weight is deliberately conservative. The idea: avoid that jump from "I never do this" to "I'm doing 5 all-out sets" that triggers the worst soreness.

When to actually worry

Normal soreness stays spread out, fairly symmetrical (both sides of the body affected similarly), and gets better day by day. See a doctor if you notice:

Extremely intense pain localized to just one muscle, along with significant swelling
Unusually dark urine (brown or cola-colored) in the days following a very intense session — a possible sign of rhabdomyolysis, a rare but real medical emergency after an unusually extreme effort
Pain that keeps getting worse past 5 to 7 days instead of easing up

In the vast majority of cases, there's nothing to worry about: it's just your body letting you know it's got some adapting to do. Move a little, eat enough protein, sleep well, and let time do the rest. Next time around, your body will be a bit more ready for it.

This article is informational and not a substitute for medical advice. In case of a health condition, pregnancy or doubt, consult a healthcare professional.

Want to go further? Browse all the Kaizmax guides. And for your tailored diet + training plan: download Kaizmax for free — a short questionnaire, ready in 2 minutes.