Sometimes muscles contract when they shouldn’t. This can be merely weird and annoying, or painful or even crippling. Although common and often unnerving, odd muscle contractions are rarely medically worrisome. There are several major types of unwanted contractions:
- Exercise-induced cramps are intense, painful contractions that usually strike when fatigued and/or overheated. They are most common in the legs, especially the calves and hamstrings, more rarely the quadriceps. Fatigue and heat are major factors, but not dehydration and electrolyte shortage (that’s a myth).
- Night cramps are a lot like exercise-induced cramps … but without the exercise! They are associated with fatigue from exercise during the day, but have many other possible causes, ranging from drug side effects to disease to iron deficiency. They mostly affect the calves and thighs, but foot arch cramps are much more prevalent with night cramps than exercise-induced cramps.
- “Spasm,” as in a “back spasm,” is an informal, non-specific term often used to “explain” musculoskeletal pain.
- Dystonia is a broad class of movement and contraction disorders that cause twisting, tremors, and awkward postures that can range from trivial to crippling, and have many causes from psychogenic to tranquilizer withdrawal to neurological diseases. There's a lot of overlap between dystonia and everything else mentioned here. Torticollis (wry neck) is the most common specific example of a classic dystonia; vaginismus is another good example (more below). Restless leg syndrome is considered a sleep disorder; it has a strong sensory component, but also a strong dystonic quality.
- Spasticity is like slow-motion cramping, usually caused by neurological diseases: a combination of jumpy reflexes and very tight muscles causing awkward and stiff movement and partial paralysis in severe cases. A good clinical example of spasticity is the “multiple sclerosis hug,” a painful, suffocating spasticity of the trunk muscles that may feel like a tight band around the ribcage. Myotonia is a rare sub-type in which contractions take much too long to relax. Spasticity has many such sub-types.
- Fasciculations (twitches) are small, brief, repetitive contractions. They occur in healthy people all the time — eyelid twitching (blepharospasm) is especially common — usually in isolated episodes like a case of the hiccoughs, sometimes dragging on longer. There are pathological causes as well; if it occurs too much with no pathological explanation, it’s “benign” fasciculation syndrome, but it can be severe in some unlucky people, like myself.1
- Clonus, despite the similarity of the term, is quite different from myoclonus: rhythmic, regular, fast repeated contractions triggered by a stretch reflex. It’s often combined with spasticity, and usually a symptom of stroke or spinal cord injury.
- Myoclonus is something everyone knows: that weird startle as we're drifting off to sleep, the "myoclonic jerk." But myoclonus can be much nastier, and is a non-specific symptom of several neurological disorders. It doesn't fit well into any of the categories about. You could consider it a fasciculation (twitch), but it's a bit too large and mean for that. And you could call it a dystonia — that's a nice broad category. But it mostly comes and and goes too fast to have much in common with the other dystonias.
- Tremors are a huge category of involuntary muscle activity, ranging from the trivial to the disastrous, from teeth chattering in the cold to the wobbles of Parkinson’s Disease. Essential tremor is the largest subcategory and most common of all movement disorders, including lots of harmless episodes in healthy people (often stress induced). Tremors are usually classified as occurring either at rest or when trying to use the muscle.
- Myokymia is fatigue-induced muscle rippling and quivering, which occurs in healthy people occasionally, and pathologically in people with “rippling muscle disease” (a bad CAV3 gene).
- Trigger points (muscle “knots”) are hypothetical mini-cramps: a small area of muscle tissue that are abnormally contracted, causing sensitive spots associated with aching and stiffness. However, this model of them is speculative and the pain and sensitivity may have nothing to do with muscle contraction.
- Tetany is sustained contraction caused by hyperactive motor nerves with many possible causes, but by convention it usually refers to hypocalcemic tetany (low calcium, which in turn is most often caused by hypoparathyroidism and vitamin D deficiency). Intriguingly, tetany can be easily self-induced by hyperventilation (alkalosis), causing the hands, feet, and mouth to claw up and tingle.2 Exactly what distinguishes tetany from other kinds of cramping is a bit murky, because the word has been adopted from the effect of tetanus infection,3 but is now applied to similar kinds of cramping (but mostly just the hypocalcemic kind).
- “Stiffness” is a symptom, a subjective feeling of restricted movement, which may or may not involve actually limited range of motion. People with dystonia feel stiff because they actually can’t move properly. But hypermobile people can also feel stiff! Stiffness is basically a kind of mild pain, a discomfort with movement with many possible causes other than unwanted muscle contraction. See Why Do Muscles Feel Stiff and Tight?
- Vaginismus is a regionally specific form of myotonia/spasticity, no different than what can happen anywhere else in the body, but it is clinically and culturally distinctive.4 It deserves emphasis because medical ignorance and mismanagement is widespread for sexist reasons. Dr. Jen Gunter devotes a chapter to this topic in her excellent book, The Vagina Bible.5
Important reassuring public service announcement: twitching and tremors rarely indicate a serious problem
Nearly all twitches and tremors are harmless and will never be explained. Like fatigue or abdominal pain, they are classic “non-specific” symptoms with endless possible causes. Un-like most other non-specific symptoms, they seem specific, and so they often freak people out. But they rarely indicate any serious pathology, and are commonly caused by:
- obvious things like stress, anxiety, fatigue, excessive caffeine and “other” stimulants
- increases in neuromuscular irritability, which occur with many relatively minor pathologies, possibly so minor that there aren’t even any other symptoms, and you’ll just have to chalk it up to …
- the weirdness of biology
This is not to say that tremors and twitches are never a symptom of something more serious, of course. But in the absence of other worrisome signs and symptoms, the odds are overwhelmingly in your favour.
Pet Theory: Our motor control systems are fantastically complicated and delicate, and smooth operation of our muscles is the result of a miraculous balancing act that gets a little off kilter surprisingly often. And yet there are also so many checks and balances that it’s hard to throw it off a lot. This may be why unwanted contractions are so common and yet usually trivial.
Muscle contraction basics
The molecular machines that power muscle tissue are bundles of Velcro-like threads of proteins — but very feisty Velcro! Imagine if a strip of Velcro didn’t just stick, but all the hooks flexed in one direction, let go, grabbed again, flexed again, and so on, one half crawling on the other like an inchworm. That’s how the proteins do it, but at the dazzling speeds of the world of molecules. Multiply their microscopic crawling action by a zillion, and you get a macroscopic muscle contraction. For more about this amazing mechanism, see Micro Muscles and the Dance of the Sarcomeres.
The biochemistry of contraction is so complex that there’s still much that we don’t know about it6 … and plenty that can go wrong, some of it probably extremely subtle.
What’s even normal? Muscle behaviour is bizarre
To understand dysfunctional or pathological muscle behaviour, it’s important to understand normal muscle behaviour, so it’s too bad that we don’t. In addition to the deep microscopic mysteries about the biochemistry, there are serious outstanding scientific questions about things like:
- how “backwards” contractions work
- why muscle tissue gets sore when we exercise it (and why wearing out one muscle might make other muscles tired7)
- how stretching increases flexibility8
Even something as seemingly simple as “normal muscle tone” is an elusive concept.
What’s a “spasm,” as in “my back is spasming”?
All known kinds of pathological contractions fit into one of the categories listed at the top of the article, like exertional cramps, spasticity, or dystonia. And yet a “back spasm” probably isn’t any of those things. It’s probably just a way of describing what back pain feels like … not what it actually is.
Unexplained musculoskeletal pain — especially back pain — is carelessly attributed to “spasms” by practically everyone. It’s a vague non-diagnosis with strong emotional appeal, which has been cynically exploited by pharmaceutical companies to sell muscle relaxants, which don’t work (covered below). It’s appealing because it’s simple and a lot of body pain just feels like a spasm, possibly because strong contractions may occur in the presence of pain with other causes.
Three major assumptions about “spasm” are often blended:
- spasms hurt — they are a major mechanism of pain, especially in the back and neck
- spasm is often “protective” — muscle guarding or splinting
- painful spasms cause themselves — a pain-spasm-pain vicious cycle
All of these are repeated ad nauseum by both clinicians and amateurs.9 Among the academics and experts, there’s a long, erratic history of debate over almost zero data, fighting over scraps. No one actually knows if they are true, and there’s a good chance they are not.
For many years I denounced them as myths, or misleading half truths at best. My contrarianism was overconfident, and based mainly on my deep distrust of vague claims. They smell like myths … but I can’t actually refute them with good evidence, because there is no such evidence. At best I can point to some red flags. Here are some basic concerns:
- Cramps are obviously painful, but so is the visible contraction of the muscle and its effect on joints. If back and neck pain are caused by contracting muscle, why can’t we see it contracting? And why aren’t we actively fighting to keep the muscle elongated, as we must with cramps?
- If pain and spasm cause each other, why wouldn’t the vicious cycle escalate at least to the point of being an obviously contractile phenomenon like a cramp? It seems like it must either be so limited that it’s not very “vicious,” or it simply doesn’t happen. (And there is direct evidence against it.10)
- “Protective” muscle spasm clearly does not make biological sense with many injuries. For instance, it would be dangerous to strongly contract the muscles around a fracture: it would tear it apart!
Although those warning signs exist, there are also clinical clues that there are kernels of truth to these ideas about “spasm,” and it’s generally unwise to underestimate the complexity of muscle physiology and motor neurology. As with so much else in medicine, the truth is simply unknown. I explore the uncertainties as best I can throughout the rest of the article.
So what would cause sharp back pains, if not “spasm”?
Descriptions of back pain like “back spasms” and “throwing your back out” are just poetic, informal ways of labelling a sudden, intense onset of back pain … which can have many causes. And figuring out the cause of back pain is one of the trickiest problems in all of medicine, which is why I’ve written so much about it over the years (including a whole book, see Complete Guide to Low Back Pain).
Sudden-onset back pain is a distinct type of back pain, and yet it still has many possible causes. People tend to think that the sharpness of the pain suggests injury or some specific mechanism — like spasm — but pain sharpness is less informative than you might think. Back pain often seems spasm-y probably because of our strong, muscular reaction to the pain: clenching and bracing! But these are reactions to the back pain, not the cause. The sensation of acute stiffness — which is complex, but basically boils down to uncomfortable movement — can also seem like muscle spasm.The tricky idea of painful spasms
Can muscle contraction hurt? Is a lot of pain caused by contracting muscle? Cramps are certainly painful and thoroughly unsubtle. You can usually see cramping muscles bulging and flexing. They literally bend people out of shape and have to be fought with urgent stretching. Bad ones can be too strong to fight, and the worst can literally rip your muscles off the bone. The pain of a cramp is a warning of imminent trauma.
If there is such a thing as a painful spasm that is not a cramp, it must be an odd beast: strong enough to hurt a lot, but otherwise undetectable. How can a contraction be strong enough to hurt without the obvious bulging, flexing, and bending of a cramp? It’s not clear.
One simple explanation is that “spasm” is often just a way of saying “it hurts” while casually implying an incorrect explanation for why it hurts. And there are some obvious reasons why we might suspect contraction — stiffness and impaired movement around pain and injury. Three evidence-based points:
- Digging into the archives, a 1989 editorial decries the “preposterous” spasm diagnosis, describing “overwhelming evidence that skeletal muscle spasm is nonexistent.”11 Unfortunately, the author only mentions one 1950 study (which I can’t find), and a replication of it that he was involved in (which I also cannot find). But giving him some benefit of the doubt, he describes a study of 50 people with neck and/or shoulder discomfort, none of whom “had EMG evidence of muscle activity in the area of pain or in the proximal paraspinal muscle.”
- During my massage therapy career, I massaged hundreds of people who believed they had “spasms” that I couldn’t detect with my experienced hands, hands that could easily detect many other subtle things. In a more formal test, two doctors trained in manual medicine could not even identify the side of the body that neck pain was on by feel.1213 A neck muscle spasm so subtle that it defies detection even with direct, hands-on inspection cannot possibly involve much contraction.
And one more thing about massage: if they’re caused by spasms, shouldn’t massage help a lot more than it does? I’m just asking!14
- Anticonvulsant drugs (like Lyrica) appear to be at least partially effective for spasticity/dystonia, but definitely do not work for back pain,15 suggesting that back pain is not normally caused by gross spasticity/dystonia.
But the truth is probably in the middle here. High muscle tone and a hardened, ropy texture are common in humans.16 In some cases, muscle tone may get high enough to be uncomfortable and “spasm” might be a reasonable way of describing it, albeit a little dramatic.
It’s a short hop from higher muscle tone to the more extreme and instructive example of spasticity — the name given to chronic contractions caused by some diseases. Not all of these are obvious, as with the “multiple sclerosis hug”: suffocating pain caused by complex dystonia of the muscles of the chest. The contractions aren’t obvious, but they cause great suffering. It’s clear from this example that rogue muscle behaviour can be painful without the nature of the problem being clear. “Spasms” seems like a fair way to describe that situation.
And could there be analogous discomfort in the neck or back? Maybe. Unfortunately, and rather incredibly, no one knows.
Protective muscle spasm (aka “muscle splinting”)
It’s also not clear that there is any such thing as a “protective” muscle spasm or “muscle splinting.” Muscle has a large behavioural repertoire, reacting in many ways to many different situations. There are undoubtedly competing and confused reflexes: situations where the body isn’t quite sure how to respond, and handles it differently over time and as conditions change. But a strong contraction around fragile tissue is a bad idea! You do not want muscles attached to a badly broken bone to spasm. Powerful contractions would injure healthy tissue!
What’s more likely? I can think of at least three plausible muscle behaviours that are “protective” without being “spasms” per se, or even the opposite:
Shutdown! A tool the nervous system almost definitely uses to keep you safe is “inhibition,” protecting the injured area more by shutting it down than by tightening it up.17 The brain and spinal cord can decree that you simply aren’t going to move a joint until further notice, period, end of discussion, not a negotiation but a strict and powerful command: “DO NOT #%[email protected]!$ MOVE THAT.” You aren’t going to blast through a movement ban like that with will power. And such a lockdown — a perfect inability to move a body part — might well feel like “spasm,” when in fact it’s literally the opposite.
“But it feels like spasm.” Yes, it does: but remember that stiffness is another imprecise word, and it describes a subjective sensation, a cousin of pain, not a specific physical state. Your brain’s reluctance to activate muscles manifests as a limited range of motion and the sensation of stiffness. It’s what “I can’t go there!” feels like.
- Flinching away! Another possibility is that protective spasm might function like a protective reflex: a strong, sudden contraction that stops you from proceeding in a potentially dangerous direction. Basically flinching away from something dangeous, except that the danger is inside you. Such contractions would be closely linked to pain: you try to move a certain way, and it hurts and your brain decides to yank you back from where you were headed with a sudden contraction … to prevent it from hurting even more! This is only a protective “spasm” insofar as it’s a sudden and not-up-to-you contraction, but it’s not a sustained “splinting” contraction either. And yet it does still seem reasonable to call it a “protective spasm.”
- Holding! Maybe there is a type of contraction that causes rigidity-without-shortening. “Isometric” contractions are contractions without movement, but this involves balanced contractions — quads and hamstrings contracting simultaneously to prevent movement — or matching an external force, and such a contraction would still be very hazardous around a broken bone. But perhaps there’s another way to contract without movement. I don’t know if this is actually possible, but there are reasons to suspect it, and muscle is definitely complex enough for such peculiar behaviour.
Tight and stiff — do they mean anything?
Our muscles can never be truly relaxed, short of paralysis. Living muscle is always on the job. There is a baseline level of mild contraction applying continuous tension to all our tendons, holding us together even when we are completely at rest. Contraction is not on/off, but a matter of degree, and the same muscle tone may be more or less functional in different ways for different people in different conditions.
And so the idea of “normal muscle tone” cannot be defined, or even be objectively measured. There is no tensionometer. What about subjective measurement, like when your massage therapist says you’re “tight”? Surely if anyone can detect muscle tension it’s a massage therapist! But no, not really: there’s a wide range of apparently healthy muscle texture; it seems to be only loosely related to any common aches and pains and stiffness, and devilishly difficult to assess. See You’re Really Tight.
Can you feel your own tightness? Probably — you can sure as hell feel a cramp! And many other pathologies that involve unwanted contractions.
And yet “stiffness” usually doesn’t describe a tissue state — it’s just a subjective feeling, a symptom, which correlates poorly with anything measurable (like a reduced range of motion). It’s likely that stiffness is more like a form of mild pain, and is a terrible way to judge muscle tone. See Why Do Muscles Feel Stiff and Tight?
The anaesthesia paralysis myth
It is a myth that muscles go completely limp during anaesthesia. They are not paralyzed. “There is a constant battle to relax the muscles during some procedures,” explains Dr. Steven Levin. The supposedly “paralyzed” muscle shrinks about 20% when cut. The tone is mediated by the brain and spinal cord. Some believe there is some intrinsic regulation of tone — that is, the muscle sets its own tone — but Dr. Levin directly refutes this with some pretty sound logic:18
Curare works at the neuro-muscular synapse, so it is the CNS that maintains the muscle tone, including the resting muscle tone (RMT). In my many years of doing surgery, I have never cut a muscle that did not retract unless it was curare-ized (and even then there is some contraction), so the tone has to be a primitive function, maybe some of it spinal, present even in deeply anesthetized creatures.
The take-home message here is that muscles are almost always contracting to some degree.
Exercise-induced cramps (and yet another myth)
Infamously for those who have followed performance science over the last 20 years or so, cramps are not caused by electrolyte loss or dehydration,192021 acute or chronic.22 What actually does cause them is still unclear (shocker). Here’s what little is known:
- Strains or “pulled muscles” can occur without any fatigue at all, but they do occur more often when you’re fatigued.23
- And of course you’ll get fatigued more quickly if you’re not conditioned for the activity.
- Some people are more vulnerable to it than others, and that vulnerability runs in families a bit
- The central nervous system is definitely involved.24
- And cramps can occasionally be so powerful that they tear muscle, though usually not very badly.
And that’s about it. There’s so much we still don’t know: for instance, weirdly, we don’t actually have a good explanation for why cramps hurt (even minor ones hurt, even when there’s nowhere near enough force involved to damage the muscle). And even muscle fatigue itself is something of a biological mystery.25
Hotshot in the dark: a spicy new cramp treatment?
Biologically plausible? Check. Credible scientists on board? Check. Actually tested? Um …
Do we really have a cool new cure for athletic cramps? Have they been “un-invented”? And wouldn’t that be great?! Or … is it just another case of putting the marketing cart before the science horse? A good article from Dr. David Colquhoun about Hotshot anti-cramp product breaks it down for us:
[Hotshot provides] three references, two are to unpublished work. The third is not about Hotshot, but about pickle juice. … [the pickle juice results] are sufficiently suggestive that it might be worth testing Hotshot properly. One might have expected that would have been done before marketing started. It wasn’t.
And it still hasn’t been done (as of early 2018). Shocker.
The other critical point Dr. Colquhoun makes is that “it’s well known that nobody understands cramp.” Indeed, we just do not have a good grip on the biology of that malfunction, which makes it tough to treat. While it is possible to stumble on a cure for a mysterious problem — such things have happened before in the history of medicine (e.g. lithium jumps to mind) — most shot-in-the-dark treatments never pan out. So, wake me up when there’s good trial evidence.
Meanwhile, being prone to cramps myself, I look forward to trying some for kicks. Not that my personal experience with it will matter one whit. As Dr. Colquhoun points out, “There can be no condition more susceptible than muscle cramps to self-deception because of regression to the mean.”26
Myokymia: fatigue-induced muscle rippling and quivering, a fascinating muscle phenomenon
Muscle fibres do not normally contract all at once, as most people imagine. Instead they are organized into groups called “motor units,” one per motor nerve. Rather than firing all at once, the groups alternate their contractions, like pistons. At any given time, countless motor units are in different phases of contraction and relaxation. The units are so small and the switching system is so fast that their coordinated action seems to be completely smooth to us.
There is an interesting exception, though: if you get tired enough that a lot of motor units start failing to contract, the switching system fails because there aren’t enough motor units available for smooth contraction. This is why muscles start to ripple and quiver with intense exertions.
It’s a difficult thing to describe! Like thin bands of muscle twitching rapidly in waves under the skin. I’ve seen a few times, and you can’t really miss it: it’s an obvious, weird thing. Usually not dramatic, but distinctive. Hat tip to reader Chris for finding this video:
That’s very similar to what I’ve seen in my own quadriceps for years now,27 but with bigger, slower waves — my ripple is at least triple that speed. The difference could just be natural variation in the phenomenon, or something else altogether, but this looks more like my own experience than anything else I’ve seen on video.
It’s called “myokymia” … sort of
There’s not quite an official name for this. The obscure term myokymia is the closest thing to the right word. Wikipedia:
an involuntary, spontaneous, localised quivering of a few muscles, or bundles within a muscle, but which are insufficient to move a joint.
That’s just right … but in practice “myokymia” is mainly used to describe a symptom of muscle disease, not a benign and temporary effect of muscle exhaustion. Another common use is as a label for harmless-but-annoying quivering of the eyelids.
Sometimes this is called fasciculation, including by yours truly for many years until I learned better. Fasciculation is just the smartypants word for a twitch or spasm, as spelled out above.
The king of controversial contractions: the trigger point
People are chock-a-block with sensitive patches of soft tissue now popularly referred to as “trigger points.” No one denies the existence of these sensitive spots, but their nature has been controversial for a century. Conventional wisdom says they are tiny pathological contractions, which is why I’m including them in this article, but they could be a more pure neurological problem.
But I doubt it. I’m not saying they definitely are contractions … but they’re probably contractions.
I am uncomfortably aware that I sound like a crank to some experts when I talk about trigger points.
It’s not proven, but I believe the evidence is good enough for a moderate degree of confidence that the clinical phenomenon known as “trigger points” is indeed related to an objectively verifiable lesion in muscle tissue, and that lesion has characteristics that are consistent with a small contracture. High confidence is not justifed by the evidence available so far … but it’s good enough to justify cautious treatment, mostly massage and self-massage. Massage can be a pleasant and rewarding experience regardless of clinical effectiveness, and self-massage is safe and cheap. In other words, it’s well worth a shot.
It sounds like such a great idea. Unfortunately, muscle relaxants are surprisingly impotent. The only kind of muscle relaxant that is over-the-counter is methocarbamol (Robaxin, etc), which mostly cannot outperform a placebo in tests.2829 Even a prescription muscle relaxant like carisoprodol is so ineffective that patients will (this is bizarre) actually tense up if they are lied to and told that the drug is a stimulant.30 Clearly the brain is the boss of your muscle tone.
And what can boss your brain around? Sedatives …
The only true muscle relaxants are the sedatives, like diazepam, AKA Valium, a benzodiazepene (the best-known of several other notorious benzos like Klonopin, Ativan, and Xanax). These are the “nuclear option” — they interfere with muscle contraction, but they also interfere with a great deal else. (The barbiturates are another class of potent sedative, barely used anymore because they are so dangerous.)
Benzos involve serious risks of physical dependence and addiction, and withdrawal can be nightmarish and dangerous. Although it is possible for many people to get off benzos, many people do not get the information and help they need for that. Sadly, I have extensive personal experience with benzo withdrawal, and I’ve written about that in detail.31
About Paul Ingraham
I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter, or subscribe:
What’s new in this article?
Ten updates have been logged for this article since publication (2016). All PainScience.com updates are logged to show a long term commitment to quality, accuracy, and currency. more
When’s the last time you read a blog post and found a list of many changes made to that page since publication? Like good footnotes, this sets PainScience.com apart from other health websites and blogs. Although footnotes are more useful, the update logs are important. They are “fine print,” but more meaningful than most of the comments that most Internet pages waste pixels on.
I log any change to articles that might be of interest to a keen reader. Complete update logging of all noteworthy improvements to all articles started in 2016. Prior to that, I only logged major updates for the most popular and controversial articles.
See the What’s New? page for updates to all recent site updates.
Aug 11, 2021 — Added mentions of restless leg syndrome and myoclonus, clarified the description of clonus, and expanded on my own experience with fasciculations.
July — Added a personal anecdote about successful treatment of a chronically twitching eyelid.
2020 — Added an unimportant but really interesting citation about non-local muscle fatigue.
2019 — Added the interesting example of vaginismus and pelvic floor spasm to the list of spasm types.
2019 — Added a little more detail about cramps.
2018 — Major revisions and more to do on the topic of “spasm,” protective spasm, and pain-spasm-pain vicious cycling. Also, new sections about muscle relaxants and sedatives.
2017 — Added discussion of tetany. Expanded on personal experience with fasciculations. Several clarifications and minor corrections.
2017 — Added a note about chronic dehydration; some speculation about why unwanted contraction is common but usually harmless; clarification of the spasm myth, and more about what does cause sharp back pains. Miscellaneous other changes.
2017 — New section: “Reassurances: twitching and tremors almost never indicate a serious problem.” Also added some more detail about my own strange example of myokymia..
2017 — Miscellaneous editing and minor improvements. Added new section “The myth of painful spasms.”
2017 — Major upgrade. Tripled the length of the article, an upgrade from a sketchy stub to a proper featured article, and now an official and worthy part of the PainScience.com library. Still plenty of sub-topics to come though!
2016 — Publication.
In 2014, I had an unforgettable battle royale with a twitch in my back (latissimus dorsi) that persisted, intermittent but frequent, for… eight months. These were strong contractions that would thump away at me, like someone knocking on my back, for 10–30 minutes at a time, several times per week, often disrupting sleep. To say that was frustrating and worrisome would be an understatement. In the early stages, I thought it was possible it would cause some kind of mental breakdown, but ultimately it simply demonstrated that the brain can adapt to almost anything. Eventually that particular twitch simply went away, and I have never felt it again since.
I have a lot of experience with muscle twitching, more generally known as fasciculation, which is one of the reasons I wrote this article. It’s a part of my own struggles with chronic pain over the last several years. A random muscle goes off on me a couple times a day — delicate vibrations, erratic fluttering, or mighty cramp-like pulses. Most episodes last seconds or a few minutes at most, but a few times a year I get one that lasts for hours or days. The only consistent feature is a repeating contraction I didn’t order.
- This phenomenon is tolerated as part of a therapeutic breathing exercise known as “bioenergetic breathing.” See: The Art of Bioenergetic Breathing: A potent tool for personal growth and transformation by breathing quickly and deeply.
- The disease “tetanus,” AKA lockjaw, is an infection with the bacterium Clostridium tetani, which causes powerful cramps.
- Women suffering from vaginismus often report a dramatic difference between the physical and functional size of their vagina. Intercourse can be physically impossible due to the contraction of the muscles of the vaginal wall and pelvic floor — a symptom that can worsen or improve, making it obvious that the physical limit is often significantly greater than what the muscles will allow.
- Gunter J. The Vagina Bible. 1st ed. Penguin Random House; 2019. Chapter 34: Pelvic Floor Spasm and Vaginismus; p. 297–304.
- We now know how molecular machines work in broad strokes — how “dumb” molecules can act alive, and produce orderly motion in the chaos of the “molecular storm” — and this is one of the great accomplishments of the last century of science. But many details are still missing, and the proteins that power muscle tissue are especially tricky. Difficult but highly recommended reading on this topic: Life's Ratchet.
- Halperin I, Chapman DW, Behm DG. Non-local muscle fatigue: effects and possible mechanisms. Eur J Appl Physiol. 2015 Oct;115(10):2031–48. PubMed #26330274 ❐
Wear out your glutes or pecs … feel it in your cloits n dloits? Some experiments has been able to demonstrate this weirdness, others have not, and so it’s ontologically ambiguous (see Behm). If it exists, it seems to involve multiple pathways: “neurological, biochemical, biomechanical, and psychological.”
And, if it exists, it obviously has Interesting Implications. If muscles you didn’t even exercise can feel exhausted, it’s equally plausible that they can also suffer other consequences. Like pain.
- Specifically, we still don’t know if it’s a neurological phenomenon, or if the tissue physically changes, or both.
- Spine-Health.com on spasm as a cause of back pain: “Muscle spasms in your back can be so painful that they may have you headed for the emergency room.”
- OxfordReference.com on “protective” spasm: “A sustained involuntary muscle contraction that occurs after injury to the muscle as a protective mechanism to prevent further movement. Such spasms commonly result in muscle stiffness.”
- MassageMag.com on pain-spasm-pain: “By applying heat and compression simultaneously to muscles that are locked in the pain-spasm-pain cycle, massage engages four separate pathways that reduce pain, decrease spasm and increase circulation.”
Claims like this are legion. They are literally never supported.
- Birznieks I, Burton AR, Macefield VG. The effects of experimental muscle and skin pain on the static stretch sensitivity of human muscle spindles in relaxed leg muscles. J Physiol. 2008 Jun;586(11):2713–23. PubMed #18403422 ❐ PainSci #53112 ❐ “We conclude that, contrary to the ‘vicious cycle’ hypothesis, acute activation of muscle or skin nociceptors does not cause a reflex increase in fusimotor drive in humans.”
- Johnson EW. The myth of skeletal muscle spasm. Am J Phys Med Rehabil. 1989 Feb;68(1):1–1. PubMed #2521794 ❐ PainSci #56710 ❐
- Maigne JY, Cornelis P, Chatellier G. Lower back pain and neck pain: is it possible to identify the painful side by palpation only? Ann Phys Rehabil Med. 2012 Mar;55(2):103–11. PubMed #22341057 ❐ PainSci #54321 ❐
Researchers tested two (presumably expert) examiners to see if they could detect the painful side of the neck or back by touch alone, feeling for tension in the spinal muscles. In almost two hundred patients, they identified the correct side of 65% of lower back pain and just 59% of neck pain — only slightly better than chance.
The results are underwhelming. Although they did a little better than just guessing, the results suggest that it’s difficult even for expert examiners to detect the location of neck and back pain by feel. As well, they were only attempting to detect the side of pain. Imagine how much worse their performance would have been if they’d had to identify the location more precisely, or if the pain could have been anywhere or nowhere. So they barely passed the easiest possible test, and probably would have failed a harder one and done no better than guessing.
An obvious weakness of the study is that only two therapists were tested, and so the results are inconclusive. One would still hope for a better detection, though, even from less skilled therapists.
- Spasm could be fairly evenly distributed, but probably not so much that it would fool experienced massage therapists. Most neck pain is strikingly one-sided, and it’s unlikely that related spasming would be tidily symmetrical.
- If common body pains were in fact substantially caused by spasm, then it seems like either massage should be an extremely effective treatment, which it clearly is not … or massage is not actually good at reducing muscle tone, which would really upset a lot of massage therapists! But I’m not issuing any kind of a ruling here: it’s just an interesting perspective to consider.
- Enke O, New HA, New CH, et al. Anticonvulsants in the treatment of low back pain and lumbar radicular pain: a systematic review and meta-analysis. CMAJ. 2018 Jul;190(26):E786–E793. PubMed #29970367 ❐ PainSci #53209 ❐
Fresh science! And two thumbs down for anticonvulsants (gabapentin, pregabalin) for back pain, sciatica, cranky nerve roots, based on a review of 9 trials.
Plus risks! I know this will shock you, but apparently these drugs have some side effects.
- Szeto GP, Straker LM, O’Sullivan PB. Neck-shoulder muscle activity in general and task-specific resting postures of symptomatic computer users with chronic neck pain. Man Ther. 2009 Jun;14(3):338–45. PubMed #18606558 ❐
This simple study showed that muscle tension in the neck is high in patients with neck pain when they rest their hands on a keyboard or type. The study does not show causation: the muscle tension may be a response to pain, and/or the pain might be caused or aggravated by the tension. However, the muscle is unquestionably more active.
- Nederhand MJ, Hermens HJ, Ijzerman MJ, Groothuis KG, Turk DC. The effect of fear of movement on muscle activation in posttraumatic neck pain disability. Clinical Journal of Pain. 2006 Jul-Aug;22(6):519–525. PubMed #16788337 ❐
This study of whiplash patients showed that muscle tone is inhibited, not increased, let alone spasmed. “It is likely that the decrease in muscle activation level is aimed at ‘avoiding’ the use of painful muscles.”
- Biotensegrity.com [Internet]. Levin SM. Muscles at Rest; [cited 20 Feb 17].
- Minetto MA, Holobar A, Botter A, Farina D. Origin and Development of Muscle Cramps. Exerc Sport Sci Rev. 2013 Jan;41(1):3–10. PubMed #23038243 ❐ PainSci #54733 ❐ “Dehydration (and/or cramps, motor unit action potentials, motor neurons electrolyte depletion) often is given as an explanation for muscle cramps occurring in workers and athletes, although this claim is not supported by scientific evidence.”
- Schwellnus MP, Drew N, Collins M. Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med. 2011 Jun;45(8):650–6. PubMed #21148567 ❐
Blood samples from 210 Ironman triathletes were checked for electrolytes and other signs of hydration status. 43 had suffered cramps. There were no significant differences between the crampers and the non-crampers in any of the pre-testing or post-testing. The shocking conclusion? Dehydration and electrolyte shortage don’t cause cramps — intense effort does. “The results from this study add to the evidence that dehydration and altered serum electrolyte balance are not causes for EAMC.” A nice myth-mangler of a study!
- Garrison SR, Allan GM, Sekhon RK, Musini VM, Khan KM. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2012 Sep;(9):CD009402. PubMed #22972143 ❐
This 2012 review of a few studies concluded that “It is unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps.” Amazingly, the evidence for the effect of Mg on cramps caused by exertion, disease, and pregnancy is just inadequate. It’s not really very plausible, but you’d think someone would have studied exercise-induced cramping at least, given its relevance to elite athletics.
- If acute dehydration during exertion isn’t the cause of exertional cramps, could subtle dehydration be the problem? Or could it cause non-exertional cramps? It seems unlikely. If acute dehydration doesn’t cause cramps, why would slight dehydration? It’s not inconceivable, but I don’t see much reason to suspect it either. I think people are only concerned about this as a seemingly logical extension of the common but totally bogus fear of chronic dehydration.
- Opar DA, Williams MD, Shield AJ. Hamstring strain injuries: factors that lead to injury and re-injury. Sports Med. 2012 Mar;42(3):209–26. PubMed #22239734 ❐
- Minetto 2013, op. cit. There’s a lot of complicated evidence on this, but it is clear that cramping is greatly reduced by nerve-blocks, cutting the muscle off from the central nervous sytem.
- Nytimes.com [Internet]. Kolata G. Finding May Solve Riddle of Fatigue in Muscles; 2008 Feb 12 [cited 15 Feb 20].
One of the great unanswered questions in physiology is why muscles get tired. The experience is universal, common to creatures that have muscles, but the answer has been elusive until now.
Scientists at Columbia say they have not only come up with an answer, but have also devised, for mice, an experimental drug that can revive the animals and let them keep running long after they would normally flop down in exhaustion.
For decades, muscle fatigue had been largely ignored or misunderstood. Leading physiology textbooks did not even try to offer a mechanism, said Dr. Andrew Marks, principal investigator of the new study. A popular theory, that muscles become tired because they release lactic acid, was discredited not long ago.
- The mean is always there, waiting to be regressed to!
- My rippling quads affects a large area of muscle, continuous when contracting, more prominent when fatigued but not dramatically, easily palpable, clearly visible only with the right lighting. I cannot actually feel it, unless I touch it. If it has any effect on performance, I can’t detect it: I seem to be strong and fatigue-resistant in the quads. I’ve had this for years at least, but I’m not sure how far back it goes. I’m not sure if it was always there and I just started noticing it, or if I’ve started noticing it because it’s there more. I am generally prone to cramps and fasciculations and always have been — it’s one of the reasons I wrote this article, and this entire website.
- See S, Ginzburg R. Choosing a skeletal muscle relaxant. Am Fam Physician. 2008 Aug;78(3):365–70. PubMed #18711953 ❐ PainSci #55418 ❐ “…these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain.”
- Khwaja SM, Minnerop M, Singer AJ. Comparison of ibuprofen, cyclobenzaprine or both in patients with acute cervical strain: a randomized controlled trial. Canadian Journal of Emergency Medical Care. 2010 Jan;12(1):39–44. PubMed #20078917 ❐
A study in the Canadian Journal of Emergency Medical Care compared ibuprofen and a muscle relaxant (cyclobenzaprine or Flexeril) for patients with serious soft-tissue injury in the neck. Groups of about 20 patients received one, the other, or both. Results were statistically identical for all patients. This test showed no benefit to using or adding a muscle relaxant for acute muscle strain in the neck. The study is too small to be powerful, but it certainly shows that there’s no strong advantage to muscle relaxants in a situation where they are often assumed to be an important medication, and the results are consistent with other research results.
- Flaten MA, Simonsen T, Olsen H. Drug-related information generates placebo and nocebo responses that modify the drug response. Psychosom Med. 1999;61(2):250–5. PubMed #10204979 ❐
How much does the effect of a medication depend on what you are told about it? Quite a bit, apparently! This strange and fascinating study in Psychosomatic Medicine showed that a muscle relaxant actually increases tension when the patient is told (lied to) that it is actually a stimulant. The false information is so potent — or the drug is so weak — that its intended effect is actually reversed.
It’s like a Jedi mind trick. These aren’t the drugs you’re looking for.
But the reverse was not true: even when told that they were taking a muscle relaxant (and they were), subjects did not actually relax any more than people taking a placebo … and in some cases less!
And there’s more. This study contains many odd gems, such as the bizarre fact that quite a lot more muscle relaxant was found in the blood of people who had been told that the muscle relaxant was a muscle relaxant. It appears that they literally soaked up more of the stuff from the GI tract when they believed that it was a relaxant! And yet it still didn’t actually relax them any more than a placebo.
- www.PaulIngraham.com [Internet]. Ingraham P. A Story of Benzodiazepine Withdrawal Gone Horribly Wrong; 2016 Sep 12 [cited 19 Nov 21].