How Many Muscles?

A (slightly tongue-in-cheek) tally of the body’s many muscles

750 words, published 2004, updated 2012
by Paul Ingraham, Vancouver, Canada

Articles in the Biological Literacy series are fun explorations of how the human body works. See below for a complete listing of articles in the series.

There are about 300 skeletal muscles in the human body. Sort of. It depends on how you count them.

How many really?

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: variations in muscle anatomy are discovered almost routinely.

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 honest-to-goodness bone-movers — 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!1

Pecs, delts, lats, traps, glutes, biceps and triceps, hams and quads, and let’s not forget the cloits and dloits!

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!

No, really, how many are there?

All right, all right — if you really must know, there are just shy of 700 named skeletal muscles.2

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 in my own work, 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 in the voice box, like the muscles around the eyeball, or the web 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.

There’s more?

Muscles comes in three types: skeletal (which moves us), cardiac (obvious), and smooth (not obvious).

If you include smooth muscle — the muscle of the organs — it becomes impossible to count. Smooth muscle blends with other smooth muscle, and exists at every scale from microscopic to large. 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!3

The little muscles that move our hairs, the arrector pilli, are a sub-type of smooth muscle. They aren’t exactly like all the other smooth muscle, and yet they aren’t exactly like your traps and pecs either. There’s several million of those, but, fortunately, they all have the same name.

And then of course there’s the cardiac muscle: a category of one. Unless you’re a Klingon, you have only one cardiac muscle, but hopefully it’s a big one.

The grand total

Well, this is how I calculate it. We have …

200 muscles that might get discussed in a gym
100 more muscles that are pretty obscure, but any self-respecting massage therapist still knows about them
400 more muscles that are really danged obscure, but various specialists know about them, and a handful of them are of special interest
several million hair-raising muscles
several billion smooth muscles cells blended together
exactly 1 heart muscle

So I’m going to go with a grand total of approximately 50,100,000,701 muscles, accurate to within 99%.

The Biological Literacy Series

An Introduction to Biological Literacy — Why you need to know more about your body
From Atoms to Elvis — A wide-angle look at the foundations of biology
How Many Muscles? — A (slightly tongue-in-cheek) tally of the body’s many muscles
Natural Imperfection — Evolution doesn’t care if you have back pain … just as long as you can breed
Something in the Air — A fascinating relationship between biology and the Schumman resonance
Ten Trillion Cells Walked Into a Bar — A humourous and unusual perspective on how, exactly, a person is even able to stand up, let alone walk into a bar
The Sixth Sense — Proprioception, the vital but mysterious sensation of position and movement
Ugly Bags of Mostly Water — The chemical composition of human biology
We Are Full of Critters — The human body is a colony of ten trillion co-operating cells
What Hurts You — The strange science of pain perception
The ‘Use It Or Lose It’ Principle — The importance of stimulation and movement in healing
Eccentric Contraction — A peculiar bit of muscle physiology
Oh, a flow-induced system of mechanotransduction! Of course! — A century-old mystery of bone biology was solved just a little while ago
Tissue Provocation Therapies — The laws of tissue adaptation and provocation therapies like Prolotherapy and Graston Technique

Notes

There are no such thing as cloits or dloits, of course. This is a reference to anatomy according to Strong Bad, which is hilarious, and included here entirely for the sake of comic relief. Kind of like the whole article, come to think of it. I beg the indulgence of the creators of Strong Bad for using his likeness without permission — a copyright infringment for sure, but I have this (probably delusional) idea that they would perceive it as charming (rather than illegal) that I love Strong Bad so much that I would spread the word about him via an anatomy article. BACK TO TEXT
Tortora et al. Principles of Anatomy and Physiology. 1996. BACK TO TEXT
Although I’ve never been able to confirm this, I believe that smooth muscle is so-named because of its smooth appearance in a microscope. Skeletal muscle is distinctively striped (striated) due to a more regular arrangement of sarcomeres. Smooth muscle is, I believe, simply less striated in appearance. BACK TO TEXT