Anyone who knows me knows that I’m totally OBNOXIOUS about the psoas (pronounced SO-AS). My patients, of course, get the worst of it, but I’ve been known to proselytize my thoughts on this amazing pair of muscles to pretty much anyone who makes me think even for a moment that they might be listening. One of the biggest reasons I am so very obsessed is that I truly believe the psoas muscles are integral to the health of several things, chief among them the hip and spine.
In Part I of this post, I’m going to lay out the framework, including anatomy and the simple biomechanics behind how the psoas works (or doesn’t). In Part II, I’ll talk exercise, and show you some simple exercises that you can do to build more strength in the psoas.
What’s a psoas, you say? First, a little anatomy:
There are actually 2 muscles with psoas in the name: the psoas major (PM) and the psoas minor. We could get super geeky about the psoas minor another time, but for the purposes of this post I am referring solely to the psoas major.
If you take a deep look through the front of your body, ripping literally EVERYTHING else out of the way, you eventually get to the 2 psoas major muscles standing like soldiers right next to the spine…
The psoas major clings to the side aspect of EVERY SINGLE lumbar vertebra, has connective tissue attachments to the diaphragm above (a whole other conversation), the bottom aspect of the pelvis below, and then crosses the hip joint to bolt into the front of the femur (thigh bone). There’s a lot there to love.
The origin, attachments and ultimate insertion of the PM give it several unique abilities. The most obvious one, and the one that has always received the most focus historically, is the ability to flex the hip, as in progressing the leg forward as you walk or run. But over time, research has illuminated the debatably more important role of the PM as a stabilizer, in particular of the lumbar spine but also of the hip joint. (1, 2)
Here’s a cool comparison that illustrates the psoas as a spinal stabilizer. Picture a suspension bridge:
With no outside supports, the center post of the bridge would be subject to the waves below and the winds above. It probably wouldn’t stand the test of time. But engineers know this. They place cables coming out from the center beam’s highest point that serve to compress, and thus stabilize it against anything the wind or the water can dish out. The same is true of the spine and the psoas. The psoas’ attachment to the lateral aspect of the spine on each side and the front of the hips bolt the spine down like it has a set of buckles, giving it a safe compressive force that allows for resilience against any challenge life might throw at it.
Now let’s think about the psoas in light of the previous concepts I’ve laid out in “The Basics”. I’ll link to each article as I discuss so you can go back and review later.
(see Are you Intrinsically Motivated? for reference)
Remember that deep intrinsic muscles have great capacity to create PRECISE joint motion (great for arthritis prevention) whereas their more superficial counterparts complement that with brute strength and power. Precise joint motion is protective against arthritis development over time.
(see To Stretch or Not to Stretch: That is the Question)
I’ve said it before and I’ll say it again: the stiffness you perceive in your low back may not be a signal you need to stretch, but quite the opposite – it is likely a compensatory muscular “grabbing on” that is intended to protect you from a deeper instability in the joints of your spine. Because the psoas muscles are uniquely positioned as two of the most INTRINSIC muscles in the human body, they provide the stability you crave, but only if you set them up for success.
(see Set your Muscles up for Success: Defining the Length-Tension Relationship)
As I’ve discussed, a muscle’s length also dictates its inherent strength. So, if your habitual posture puts a muscle either in a LONG or a SHORT length, it will also be weak. If you’ve been educated on how to correct your plumbline posture (line your ear, shoulder, hip and ankle up one on top of the other like building blocks), you optimize the length-tension relationship of a muscle, and make it stronger just simply based on its position and length.
As if creating more inherent strength wasn’t enough of a reason to correct your posture, there’s another reason in the case of the psoas. Think back to that bridge: if you stand in a chronically swayback posture (see below) instead of providing a straight downward force to give the spine a springy, compressive resilience, in a swayback posture the psoas would be providing a constant backward-buckling compressive force. Ouch! Down comes the bridge.
The implication of this buckling force is pain, which can manifest in standing and walking activities or maybe even in sitting when the shoulders are behind the hips. Your doctor might order an xray that would inevitably demonstrate arthritic change and use terrible scary words like “facet joint arthrosis” and “degenerative joint disease (DJD)”. You might be told it’s “normal wear and tear for your age”, as if you have no control whatsoever over how much you wear or how much you tear. OR, you might think “Well that arthritis is from good old Dad. You can’t escape your genes!” Really?! Let’s be better than that. Maybe what you inherited from Dad wasn’t arthritis but learned postural dysfunction. Here’s your empowerment lesson for the day: what is learned can also be unlearned.
Psoas I was saying… the psoas can be your best friend or your worst enemy. It will compress you either way, but you have the power over whether that compression causes harm or good simply by consistently correcting your posture. Any exercise to strengthen the psoas from there is just icing on the cake.
- Manuelle Therapie. 2007. 11:177-187
- Journal of Orthopaedic Science. 2002. 7: 199 – 20
The Movement Mama 