Muscle soreness: what really causes it, and what eases it?
Key points
- Muscle soreness is not caused by lactic acid. Lactic acid (more precisely, lactate) clears from the muscle shortly after exercise, while soreness only starts the next day.
- Soreness comes from micro-tears in the muscle fibres and the body's repair process. It is typically strongest 24–72 hours after training.
- It is mostly caused by unfamiliar movement and braking (eccentric) work: downhill running, walking down stairs, lowering a weight slowly.
- What can ease it: light movement, enough sleep, protein, and massage, which research ranks among the most effective methods for reducing the feeling of soreness.
- With a massage gun on a sore day: low speed, 1–2 minutes on a large muscle, and don't pound the most painful spot.
- Soreness is not a measure of a good workout: if it is strong after every session, that points to too big a jump.
Contents
- Is lactic acid really the cause of muscle soreness?
- What happens in the muscle after training?
- How long does muscle soreness last?
- What eases muscle soreness?
- Massage gun for sore muscles: how to use it
- Cold or heat for sore muscles?
- How to prevent the next bout of strong soreness
- Black Friday 2026: Elit Massage Gun in the Black November bundle
On Monday you went back to training after a long break. Tuesday, nothing yet, but on Wednesday you have to hold the handrail going down the stairs. That is muscle soreness, and most people still blame lactic acid for it. Yet by then, the lactic acid is long gone.
In this article we look at what actually happens in the muscle, how long it lasts and what really eases it. We also cover how to use a massage gun on sore days, because your muscles need something different then than after an average workout.
Is lactic acid really the cause of muscle soreness?
No. Lactate (what people commonly call lactic acid) does build up in the muscle during intense exercise, and it causes the burning feeling during training. After training, however, it clears or is used up by the body within a short time, typically within an hour. Muscle soreness, on the other hand, only starts 12–24 hours later and lasts 1–3 days. The two don't even line up in time.
The lactic acid explanation is so persistent because it is simple and easy to picture. The problem is that it points you in the wrong direction: if you try to get rid of the acid, you are not focusing on what actually helps. Muscle soreness is not about a substance, it is about the muscle needing time and repair.
What happens in the muscle after training?
Unfamiliar or heavy load causes tiny injuries, so-called micro-tears, in the muscle fibres. The body responds with a repair process: more blood, fluid and repair cells flow to the area, and nerve endings become more sensitive. That is what you feel as soreness. At the end of the process the muscle is stronger, which is why the same workout hurts less next time.
The strongest soreness comes from braking, eccentric work, when the muscle works while lengthening. Examples are running downhill, walking down stairs, lowering into a squat or lowering a weight slowly. This is why your thighs hurt more after a hike with a lot of downhill than after a longer run on flat ground.
Unfamiliarity matters just as much. The first session after a break, a new exercise or a new sport always comes with more soreness. Your body adapts within 1–2 weeks, which is known as the repeated bout effect.
How long does muscle soreness last?
Muscle soreness typically starts 12–24 hours after training, peaks between 24 and 72 hours, and fades within 3–5 days. If it lasts more than a week or keeps getting stronger, it may no longer be simple soreness, and it is worth asking a professional for their opinion.
| Time after training | What you feel | What to do |
|---|---|---|
| 0–12 hours | Tiredness, but hardly any pain yet | Cool-down, food, fluids, early night |
| 24–72 hours | Muscle tender to pressure and stiff, the first movements hurt | Light movement, massage at low intensity |
| Days 3–5 | Tenderness easing | Gradual return to normal training |
What eases muscle soreness?
You can't make muscle soreness disappear in a day, but you can ease how it feels and support your recovery. What matters most: light movement with the sore muscle, enough sleep, enough protein, and massage. A 2018 meta-analysis (Dupuy et al., Frontiers in Physiology) found massage to be the most effective of the methods studied for reducing the feeling of muscle soreness.
- Active rest. 20–30 minutes of walking, easy cycling or swimming on a sore day. This brings more oxygen and nutrients to the damaged fibres, and the stiffness at the start of movement eases sooner.
- Sleep. Most of the muscle repair happens at night. 7–9 hours of sleep is not a luxury, it is part of recovery.
- Protein. Muscle repair needs building material. Spread your daily protein evenly, and eat some protein within a few hours after training.
- Massage. By hand, with a massage gun or with a cupping device. This helps the tight, tender muscle relax and makes movement easier.
Our view: on a sore day, complete rest should not be the goal. After a day on the sofa, you will be just as stiff on the third morning. Light movement and a short massage help more than staying still.
Massage gun for sore muscles: how to use it
On a sore muscle, use the massage gun on a low speed with a soft or ball head, and keep it moving. On a large muscle group (thighs, glutes, back) 1–2 minutes is enough, and a full session should be no longer than 15 minutes. Don't pound the most painful spot: muscle soreness is not a knot you need to break up.
- Start on the lowest speed. A sore muscle is more sensitive, so what normally feels good may hurt now. This way you can increase it gradually while it stays comfortable.
- Ball or soft head. The flat and the pointed heads are more concentrated, so save them for normal days. We wrote about what each head does in the massage gun heads article.
- Keep it moving, don't hold it in one place. Don't stay on one spot for longer than 10–15 seconds. This way you work the whole muscle and don't overload the sensitive spot.
- 1–2 minutes on a large muscle. On a sore day, less is more. You will find exact times for each body area in the how to use a massage gun by body area guide.
- Move afterwards. A short walk or a few slow squats after the massage. This way the looser muscle gets to work straight away and stays loose for longer.
The Elit Massage Gun has 30 speed levels, so on sore days you can start from a very low, gentle vibration and increase it in small steps. On normal days, its 13 mm amplitude and 40 kg stall force also reach deeper muscle layers. It comes with 20 massage heads and a 6–10 hour battery. You also get a free online tutorial: in 16 short videos, a rehabilitation specialist shows which speed, pressure and head to use for each muscle group.
Cold or heat for sore muscles?
Right after a very hard workout, cold is an option, but on sore days (24–72 hours) most people find heat more pleasant: a warm shower or a warm compress relaxes the stiff muscle and makes it easier to get moving. We wrote about the timing of ice water in the ice water after training article.
The Cryoflex gel wrap works for both: you can chill it in the freezer or warm it in the microwave, and it fits on the knee, ankle, elbow, forearm and calf. If your calf or forearm aches after training, a warm Cryoflex does its job while you sit on the sofa.
The CUPPER Cupping Device is another option: the suction lifts the skin and the surface tissues, which many people find pleasantly relaxing on large muscles. A session typically lasts 5–15 minutes. Give the same area 2–3 days of rest between sessions, and 1–2 sessions a week is enough for most routines.
How to prevent the next bout of strong soreness
You can't and don't need to avoid it completely, but you can avoid strong soreness that lasts for days. The key is progression: start a new exercise, a new sport or a comeback after a break with a lighter load, and increase it only in small steps each week.
- Make your first session easier than you could handle. After the first session, your body adapts within 1–2 weeks.
- Warm up for 5–10 minutes. Light cardio, then the main exercise with a light weight. You can also warm up with a massage gun, on a low speed, for 30 seconds per muscle.
- Dose the braking movements. Before a hike, downhill running or a new eccentric exercise, don't go to your maximum the first time.
- Soreness is not a measure of a good workout. If it is strong after every session, that points to too big a jump, not to more progress.
Black Friday 2026: Elit Massage Gun in the Black November bundle
During Black November, the Elit Massage Gun is available in the Elit Massage Gun + 4 Gifts bundle, with 4 products included: the CUPPER Cupping Device, the Cryoflex hot and cold compress, the Knee Support knee brace and the Easy Sleep Pro magnetic nasal dilator. The gun also comes with a free tutorial. MovTech's Black Friday offers are available until November 30.
- Elit Massage Gun: 30 speeds, 13 mm amplitude, 20 massage heads, with a free tutorial.
- CUPPER Cupping Device: for relaxing large muscles, in 5–15 minute sessions.
- Cryoflex: a hot and cold compress in one, for arms and legs.
- Knee Support knee brace: with 2 steel side springs and a silicone ring around the kneecap.
- Easy Sleep Pro: a magnetic nasal dilator for nose breathing at night, because most muscle repair happens during sleep.
You will find the bundle contents, the available sizes and the current price on the Elit Massage Gun + 4 Gifts bundle page.
When is it not muscle soreness, and when should you ask a doctor?
- sharp, stabbing pain already during training, at a specific movement;
- swelling, bruising or a sudden loss of muscle strength;
- the soreness lasts more than a week or gets stronger day by day;
- unusually dark urine after a very hard workout;
- the joint hurts, not the muscle.
In these cases, don't massage the area, ask a doctor for their opinion. The massage gun and the cupping device are recovery tools and are not suitable for treating medical conditions.
In summary
Muscle soreness is not caused by lactic acid but by micro-tears in the muscle fibres and the body's repair work, which is why it peaks 24–72 hours later. Light movement, sleep, protein and massage can ease it, while staying still only drags it out.
With a massage gun, go for less and gentler at times like this: low speed, soft head, 1–2 minutes on a large muscle. And you can prevent the next bout of strong soreness with gradual progression, not by skipping training.
