My favorite muscle

Each day I receive a "Word a Day" e-mail from the Wordsmith. Last week I was delighted to get a message related to my favorite muscle. Here is an excerpt from the e-mail:

sartorial (sar-TOR-ee-uhl) adjective

Related to a tailor or tailored clothes.

[From Late Latin sartor, tailor.]

Today's word has a cousin, sartorius, a long narrow muscle in the leg, the longest muscle in humans. What would tailored clothes have in common with a muscle of the leg? Sartorius is so named since it is concerned with producing the cross-legged position of tailors at work.

If you have the opportunity to dissect a cadaver, you can't miss the sartorius. The longest muscle in the human body, the slender sartorius wraps like a python across the thigh and knee, attached at one end to a large protuberance on the hip bone (the anterior superior iliac spine, or ASIS for short) and to the tibia just below the knee at the other end.

In spite of its impressive appearance, the sartorius hasn't become a household term like the more familiar "quads," "hamstrings," "biceps," and "lats." Perhaps this is because the muscle normally is buried under a layer of fatty connective tissue, and rarely stands out like the massive quadriceps next to it. Here is an extraordinary exception:


See the long skinny muscle just below the contest number on his left hip? That's the sartorius. While other people are admiring Aaron Maddron's biceps or lats, I'm thinking, "Now that's a nice sartorius!"

To be honest, I had no idea that tailors assumed a characteristic position with their legs until I learned about the sartorius. Tailors don't have a monopoly on this position. Anytime you sit cross-legged with your left outer ankle resting on your right knee (or vice versa), you're doing it too.

From an anatomical perspective, describing the actions required to cross your legs is more complicated than you might guess, so bear with me. Imagine yourself standing, face and palms facing forward, feet together, elbows and knees straight. Anatomists call this the "anatomical position." Now (1) bend your left knee; (2) lift your left knee so that your thigh makes a right angle with your trunk; (3) move that knee outward; then (4) rotate the left thigh so that your foot swings towards your right knee. Each of those actions - knee flexion, hip flexion, hip abduction, and hip external rotation - happens when you activate the sartorius on the left side. Now all you have to do is flex your right knee and hip, find a chair to sit on before you lose your balance, make sure your left leg is resting on the right knee, and you've assumed the tailor's position.

So, could you cross your legs without a sartorius? Yes, because every action assigned to the sartorius is also performed by other muscles. And it's relatively weak. Given its small diameter, the sartorius doesn't generate much force compared to its neighbors in the thigh. Perhaps its most important function is protection. In the anatomy lab, pulling the sartorius to one side reveals two major blood vessels on their way to and from the calf - the femoral artery and femoral vein. Covering those vessels with a muscle presumably offers better protection than mere skin, fat, and connective tissue.

Photo of Aaron Maddron from Thigh Masters: Men with Great Legs