Sore Muscles After Exercise: What Causes Them, How Long They Last, and What Actually Helps

Key Takeaways

• Sore muscles that appear a day or two after training are called delayed onset muscle soreness (DOMS). Soreness typically becomes noticeable about 6–8 hours after a hard session and peaks at roughly 48 hours [1].
• Lactic acid is not the cause. In a classic treadmill experiment, level running raised blood lactate without causing soreness, while downhill running caused significant soreness without any rise in lactate [2].
• How sore you feel is a poor indicator of how much muscle damage occurred, and it is not a reliable indicator of muscle growth [1].
• In a meta-analysis of 99 studies, massage was the most effective of the recovery methods compared for reducing DOMS, while stretching showed no significant benefit [3]. Evidence that massage also speeds up functional recovery is mixed [4][5]. In my view, any effect on overall recovery is probably modest, and its main benefit may be that you can return to training sooner with less pain, although the cited studies did not directly test this outcome.
• Muscle soreness or cramps and/or dark urine after heavy endurance exercise warrant screening for exertional rhabdomyolysis [6].
• From a clinical perspective, ordinary DOMS usually settles on its own, whereas pain that lasts unusually long may point to an overuse problem such as a tendon attachment problem, tenosynovitis or bursitis, and may warrant a medical assessment.
• In my own experience, soreness starts to be felt on the first day, is at its worst on the second, and becomes less pronounced the more regularly you train.

Introduction: Why Muscle Soreness Matters More Than You Think

Almost everyone who trains has woken up to stiff, aching legs after a new program, a long downhill run or a heavy eccentric session. Sore muscles are usually harmless, but they are not trivial: a narrative review in sports medicine described DOMS as a mild form of ultrastructural muscle injury and noted that it is one of the most common reasons for compromised sports performance [7].

In my clinical experience, most patients recognize this kind of muscle pain and understand that it usually passes with time and rest. It is when the pain lasts unusually long that they tend to seek help.

This article covers what actually causes sore muscles, how long the soreness lasts, which recovery methods have evidence behind them, and the warning signs that mean soreness is something more serious.

What Are Sore Muscles? Understanding DOMS

Delayed onset muscle soreness is the pain and stiffness that develops in muscles in the days after unaccustomed exercise. A classic review in Medicine & Science in Sports & Exercise placed the window at 1 to 5 days after the exercise bout [8].

The type of muscle action matters. Both concentric and eccentric training can produce soreness, but lengthening (eccentric) actions have the strongest effect, and soreness is most pronounced when the training stimulus is new to the body [1].

The same review notes that the time course is highly variable and depends on exercise intensity, training status and genetics, and that the literature available at the time did not support sex-related differences in how DOMS is expressed [1].

It is worth separating muscle soreness after exercise from office-type back pain, which can have different causes. In my clinical experience, patients often mix the two up, partly because muscle pain tends to feel much the same to them whatever its cause. Many are puzzled that their back can become sore when they have not done anything, and some, having linked the two, become afraid of loading their back. Office-type back pain is beyond the scope of this article, but it is a different situation from post-exercise soreness.

What Causes Muscle Soreness? It Is Not Lactic Acid

The most persistent myth is that sore muscles come from lactic acid “building up” in the muscle. Researchers tested this directly in 1983. Participants ran for 45 minutes on a treadmill, once on the level and once at a −10% grade, and both blood lactate and soreness were tracked for 72 hours. Level running raised lactate significantly but produced no significant soreness afterwards. Downhill running never raised lactate, yet it produced significant delayed soreness [2]. The authors concluded that lactic acid is not related to DOMS.

So what actually causes sore muscles? The honest answer is that it is still not fully settled. The 1984 review by Armstrong stated that the cellular mechanisms were unknown and proposed a model in which high tension during eccentric work causes structural damage, which disrupts calcium handling in the injured fibers, after which breakdown products accumulate and stimulate pain-sensing nerve endings [8]. A 2018 review described the primary mechanism as ultrastructural damage to muscle cells, followed by protein breakdown, apoptosis and a local inflammatory response, and attributed the delay in symptoms, with soreness typically peaking at 48–72 hours, to a complex sequence of local and systemic responses [7].

Current theory also points to the connective tissue around muscle fibers. Schoenfeld and Contreras summarized DOMS as most likely a product of inflammation from microscopic tears in connective tissue that sensitize pain receptors, with swelling adding further pressure [1]. Interestingly, they also cite work showing that people can experience severe DOMS without measurable local signs of inflammation [1].

How Long Do Sore Muscles Last?

Reported time frames vary slightly by source: onset at about 6–8 hours with a peak near 48 hours [1], peak soreness at 48–72 hours [7], and an overall window of 1 to 5 days [8].

Importantly, the performance drop that comes with DOMS is temporary. Armstrong noted that DOMS can reduce performance both because people voluntarily hold back and because the muscle temporarily loses force capacity, but that permanent impairment does not occur [8].

In my own experience, DOMS starts to be felt during the first day and is at its worst on the second day, which fits the roughly 48-hour peak described above. After a heavy squat session, for example, walking down stairs is often hardest on day two.

From a clinical perspective, muscle pain after exercise can roughly be divided into two categories. The first is ordinary DOMS, which usually passes on its own and is largely a physiological response. The second is a less common, longer-lasting problem that I see from time to time after excessive training: the muscle itself may be overloaded or injured, or the pain may come from a tendon attachment problem (enthesopathy), tenosynovitis or bursitis. In my experience, patients often recognize that this pain is different from their usual post-exercise soreness, link it to unusually heavy loading and avoid sport while it is painful, and for some this can take up to a week, although the underlying cause cannot be determined from symptoms alone. In the patients who come to see me because the pain has persisted unusually long, it is often one of these overuse conditions of the attachment tissues.

Does Soreness Mean You Had a Good Workout?

This is where many athletes go wrong. Having sore muscles is linked to muscle damage, but it is a weak measuring stick. In their review, Schoenfeld and Contreras reported that soreness ratings correlate poorly with both the time course and the magnitude of accepted markers of muscle damage, including strength loss, range of motion, limb swelling and blood creatine kinase [1].

The link to muscle growth is even weaker. The same authors point out that marathon running and long-duration cycling can cause marked soreness without producing meaningful hypertrophy, and that research has shown muscle damage is not obligatory for muscle growth [1]. They concluded that soreness has limited value for judging workout quality, and that high levels of soreness should be seen as detrimental rather than desirable [1].

Among athletes, DOMS is very common after hard or unusual training sessions, and it has traditionally been treated as a gauge of how hard you trained or how much work you did. For a long time, I held the belief that if my muscles did not get sore, I had not trained properly, in the same way that if I was not out of breath, the session did not really count. Looking back, that thinking did not make a great deal of sense. Soreness may follow demanding work, but it does not reliably show how much productive work was done.

If you want to understand what actually drives muscle growth, see our article on what actually causes muscle growth.

Soreness is also not the same thing as a blood marker of muscle breakdown. For athletes who have had blood work and seen a high CK value after training, our guide to elevated creatine kinase after a workout explains how to interpret it.

Why Soreness Fades Over Time: The Repeated Bout Effect

Sore muscles are usually much less of a problem the second time you do the same exercise. Armstrong already noted in 1984 that training the specific type of muscle action that causes DOMS reduces the soreness response [8]. This protective adaptation is known as the repeated bout effect.

The protection can last a surprisingly long time. In a study of 35 male students who performed two bouts of eccentric elbow flexor exercise, the repeated bout effect for most measures lasted at least 6 months but was lost between 9 and 12 months [9].

Schoenfeld and Contreras noted that training a muscle group frequently reduces soreness yet could still produce substantial hypertrophy [1].

In my own experience, DOMS becomes less pronounced the more and the more often I train, which in turn makes training easier. This fits well with the repeated bout effect described above.

What Helps Sore Muscles? What the Evidence Shows

A 2018 meta-analysis of 99 studies compared the most commonly used recovery methods. Active recovery, massage, compression garments, water immersion, contrast water therapy and cryotherapy all produced small to large reductions in DOMS (Hedges’ g from −0.40 to −2.26), while the other methods studied showed no change [3]. The key findings:

• Massage was the most effective method for reducing both DOMS and perceived fatigue, with the largest effect on soreness (g = −2.26) [3]. For more on this, see our article on sports massage for recovery.
• Compression garments and water immersion reduced DOMS and perceived fatigue, but less than massage [3]. In a temperature subgroup analysis, only immersion in water below 15 °C had a positive effect on inflammation markers, although the overall immersion analysis showed no significant change in blood IL-6 or CRP [3].
• Active recovery reduced DOMS but did not change perceived fatigue [3]. Armstrong had earlier observed that muscular activity seemed to be the best treatment, although the soreness returns after the activity stops [8].
• Cryotherapy reduced DOMS within the first 6 hours after exercise, but the effect was not present at 24 hours or later [3].
• Stretching and electrostimulation had no significant effect on DOMS or fatigue [3]. Read more in our guide to stretching for athletes.

Two caveats matter. The meta-analysis examined only a single recovery session, and because participants cannot be blinded to massage or immersion, a placebo effect could not be ruled out [3].

In my clinical experience, patients most often turn to massage and stretching for help. Massage does reduce DOMS, and in the meta-analysis above it was the most effective method studied [3]. Whether it also speeds up functional recovery is less clear. One meta-analysis of 11 randomized trials, all of low quality, found that massage after strenuous exercise improved maximal isometric force [4], whereas a larger meta-analysis of 29 studies found no evidence that massage improves strength, jump, sprint, endurance or fatigue [5]. In my view, any effect on an athlete’s overall recovery is probably modest, and its main practical benefit may be that, with less pain, you can return to training somewhat sooner, although the cited studies did not directly test this outcome. Stretching appears to help even less: a Cochrane review of 12 studies concluded that stretching does not produce clinically important reductions in DOMS in healthy adults [10].

Foam rolling. A separate meta-analysis found seven studies of rolling after exercise, four using foam rollers and three using roller massage devices. Post-exercise rolling reduced perceived muscle pain by 6.0% (g = 0.47), but the authors judged the overall effects of foam rolling on performance and recovery to be rather minor and concluded the evidence better supports it as a warm-up than as a recovery tool [11]. If you want one anyway, see our review of the best foam rollers.

Painkillers (NSAIDs). A meta-analysis of studies on acute skeletal muscle injury found that NSAIDs produced a small to medium reduction in markers of muscle injury (effect size +0.34) and supported their use for reducing strength loss, soreness and creatine kinase in humans, at least in the short term [12]. The authors also noted that NSAID use appeared detrimental at later time points in animal studies but not in humans, and that this needs further research [12]. Because this research covered acute muscle injury more broadly, it should not be read as a general recommendation to use NSAIDs for ordinary, uncomplicated DOMS.

A caution about ice baths for lifters. Cold water immersion may relieve soreness, but it may not suit every goal. A 2024 meta-analysis of 8 studies concluded that cold water immersion immediately after resistance training may attenuate hypertrophy [13]. The evidence specifically concerns immersion immediately after training; the effects of later or occasional use remain uncertain. Our best cold plunge tubs article covers this trade-off in more detail.

Should You Train While Sore?

The evidence on training with sore muscles is limited. According to Schoenfeld and Contreras, training during the early recovery phase does not seem to worsen muscle damage, but it may interfere with the recovery process [1]. The same review notes that pain associated with DOMS has been shown to impair movement patterns, albeit in individuals with high pain-related fear, and that some researchers have speculated it could reduce motivation to train [1].

A practical reading of the evidence (clinical synthesis, not a tested protocol):

• Light activity of the sore muscle groups is reasonable and may temporarily ease the discomfort, although soreness tends to return afterwards [8].
• Delay heavy or high-skill work for the sore muscle group until movement quality is back to normal.
• Introduce new exercises, especially eccentric-heavy ones, gradually so the repeated bout effect can do its work [8].
• Do not chase soreness as a sign of progress [1].

When Sore Muscles Are a Red Flag: Exertional Rhabdomyolysis

Exertional rhabdomyolysis is relatively uncommon but potentially fatal [14]. Armstrong’s 1984 review described exertional rhabdomyolysis as appearing to be the extreme form of DOMS [8].

A 2023 systematic review of 25 studies including 772 patients explains that exertional rhabdomyolysis results from the breakdown of skeletal muscle cells after intense exercise, leading to raised creatine kinase or myoglobin. A urine dipstick may also be positive for blood, and kidney insufficiency is a possible complication [6]. Young men were particularly affected, with a mean age of 28.7 years. Running, including marathons, accounted for 54.3% of the cases included in the review and weightlifting for 14.8%, and mean creatine kinase at presentation was 31,481 IU/L [6]. The authors concluded that the condition seems to be underestimated and that people who present with muscle soreness or cramps and/or dark urine after heavy endurance events should be screened [6].

In practice, unusually severe pain in a particular muscle after exertion is one of the findings that raises alarm, because it brings rhabdomyolysis to mind. One of my patients, a woman who had done a hard CrossFit session with a large number of push-ups, unexpectedly developed rhabdomyolysis of the pectoral muscle. Her chest muscle was exceptionally painful, and what raised suspicion was that her urine dipstick was positive for blood. In rhabdomyolysis, myoglobin can make the chemical dipstick react as if red cells or hemoglobin were present; a clinical review describes this as positive blood findings on urinalysis without red blood cells [14]. She was referred to hospital, where rhabdomyolysis was confirmed, and she was kept under observation and given fluid treatment.

Some patients with rhabdomyolysis notice that their urine turns dark, and the condition is dangerous because of the risk of kidney failure. In addition, muscle breakdown can raise blood potassium levels, which in some patients may lead to an arrhythmia. The same review lists acute kidney failure, hyperkalemia and cardiac dysrhythmias among the severe consequences of exertional rhabdomyolysis [14].

According to the same review, affected individuals typically report pain, tenderness, weakness and swelling in the affected muscles, and elevated myoglobin will occasionally darken the urine to a tea or cola color [14]. Seek medical care promptly if soreness after exercise comes with dark urine, marked weakness or swelling. Our article on myoglobin vs. creatine kinase explains how these markers are used.

Practical Recommendations for Sore Muscles

• Expect soreness after unfamiliar work. Unfamiliar and eccentric-heavy exercise is the most likely trigger [1].
• Progress gradually. Training the same type of muscle action reduces the soreness response, and the protection can last for months [8][9].
• If you want relief, massage had the largest effect on DOMS among the recovery methods compared in a 99-study meta-analysis [3].
• Do not rely on stretching to reduce soreness [3].
• Consider avoiding cold water immersion immediately after resistance training if muscle growth is your goal [13].
• Judge your training by objective progress, not pain. Soreness tracks muscle damage and growth poorly [1].
• Know the red flags: soreness or cramps and/or dark urine after heavy endurance exercise warrant medical evaluation [6].

Conclusion: Muscle Soreness Is a Signal, Not a Score

Sore muscles are a normal, temporary response to unfamiliar or eccentric exercise. They usually peak around two days after training and are not caused by lactic acid. Sore muscles tell you that your body met a new stimulus, but they say little about how much damage occurred or how much muscle you will build. Massage, compression and water immersion can ease symptoms, and consistent, progressive training lets the repeated bout effect reduce soreness over time. The main exception to “soreness is harmless” is unusually severe pain, marked weakness or swelling, or dark urine after heavy exercise, which should prompt medical assessment.

From a clinical perspective, it helps to separate ordinary DOMS, which usually passes within a few days, from longer-lasting overuse problems of the muscle or its attachments, and from the rare but dangerous case of rhabdomyolysis. As an athlete, I long believed that a session without sore muscles did not count. Looking back, chasing soreness was not necessarily the best strategy, and in my experience it fades the more regularly you train, which in turn makes training easier.

References

1. https://doi.org/10.1519/SSC.0b013e3182a61820
2. https://pubmed.ncbi.nlm.nih.gov/27409551/
3. https://doi.org/10.3389/fphys.2018.00403
4. https://doi.org/10.3389/fphys.2017.00747
5. https://doi.org/10.1136/bmjsem-2019-000614
6. https://doi.org/10.1097/JSM.0000000000001082
7. https://doi.org/10.1055/a-0753-1884
8. https://doi.org/10.1249/00005768-198412000-00002
9. https://pubmed.ncbi.nlm.nih.gov/11528337/
10. https://doi.org/10.1002/14651858.CD004577.pub3
11. https://doi.org/10.3389/fphys.2019.00376
12. https://doi.org/10.1177/0363546517697957
13. https://doi.org/10.1002/ejsc.12074
14. https://doi.org/10.1177/1941738114523544