There are about 300 skeletal muscles in the human body. Sort of. It depends on how you count them.
It’s surprisingly hard to tell. You wouldn’t think the total number would be ambiguous, but it’s difficult to know what to include and exclude, and anatomists don’t always agree. Some muscle tissue really can’t be separated into countable muscles. And, believe it or not, the science of anatomy is still advancing. No, entirely new muscles aren’t being discovered — but novel variations in individual muscle anatomy are found more or less constantly,1 and supernumerary muscles — extra muscles — are not unusual.2 Many muscles, like the four-part quadriceps, are normally split into different parts that may or may not traditionally count as separate muscles3 — but then some people’s muscles are more divided than others. It makes a firm count just about impossible.
There are only about 200 muscles that anyone, even a massage therapist, might actually be interested in knowing about. When most people ask how many muscles are in the human body, they mean the serious bone-movers — Pecs, delts, lats, traps, glutes, biceps & triceps, hams & quads & let’s not forget the cloits & dloits!muscles that do real work, muscles like pecs, delts, lats, traps, glutes, biceps and triceps, hams and quads, and let’s not forget the cloits and dloits!4
There are maybe another hundred muscles if you include the fiddly little muscles of the hands and feet, and the major face muscles. In school, I had to learn the Latin for all them!
All right, all right — if you really must know, there are just shy of 700 named skeletal muscles.5
But that’s including about 400 muscles that, mostly, no one cares about except specialists. I am aware of a few that have clinical importance to a massage therapist, but I’m mostly just barely aware of their existence — like the smaller facial muscles, like the mess of little muscles around and under the tongue and around the voice box, like the muscles around the eyeball, or the crazy trampoline of muscles on the pelvic floor.
But believe it or not, although that’s all of the muscles you can count, that’s still not all of the muscle — not even close.
Muscles comes in three types:
If we include smooth muscle in our census, the job becomes truly impossible. Smooth muscle is the muscle of organs, the muscle that does the work of the autonomic nervous system, squeezing and squishing stuff in tubes mostly, but also raising hairs, focussing eyes, raising hairs,6 and pushing out babies.7 Smooth muscle blends with other smooth muscle, and exists at every scale from microscopic. You have single cells of smooth muscle wrapped around capillaries, and you have organs like your stomach that are wrapped completely in three thick layers of smooth muscle. It’s impossible to say where one smooth muscle stops and the next begins. Perhaps that’s why they call it smooth.8
At the other counting extreme, of course there’s that singular cardiac muscle: a category of one. Unless you’re a Klingon or a Time Lord, you have only one cardiac muscle, but hopefully it’s a big one.
This is how I calculate it. We have …
So I’m going to go with a grand total of approximately 50,100,000,701 muscles, accurate to within 99%.
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
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— Substantial miscellaneous improvements. Added a couple notable citations about anatomical variations. New featured image.
This dissection study of 275 dead buttocks found that 6.4% of them had variations of sciatic nerve and piriformis muscle anatomy, with considerable variety in the variation. They found several different arrangements, and concluded: “Some rare, unclassified variations of the sciatic nerve should be expected during surgical intervention of the region.” Prepare to be surprised, surgeons!
All of these differences are potentially clinically significant, probably especially in the cases where the nerve (or part of it) passes right through the muscle. For a couple case studies, see Arooj 2014 and Kraus 2015.BACK TO TEXT