The Psoas: Is it the most important postural muscle?

[Editor’s note: This is a guest post by Nadine Fawell who blogs at Yoga with Nadine. Check it out!]

Well, I think it is anyway. There are many, many reasons I think this: I could practically write a BOOK about the psoas.

But here’s something to think about.

When we went from walking on four legs to walking on two, we had to find a way to hold our upper bodies, well, up.

In four-legged creatures, the spine is happily suspended between front and back ends. In our case, it pokes up into the air. Our back muscles and belly muscles, and most especially our buttocks muscles had to get a whole lot stronger to hold us up that way.

We developed a gluteus maximus on each side of our butt (that muscle is just called gluteus superficialis in four legged animals). Its main job?

To hold us upright by bringing our hips into extension (backbending). That’s why it’s so big. It has to be, to defy gravity.

See, in this picture:

I am bending backwards and you can see my, erm, gluteus maximus, is working, yes?

I only look so happy, though, because I know I can contract my psoas muscles in the front of my hips to oppose the action of my butt and return me to an upright position.

The psoas is a deep muscle in the front of our hips, which hooks our spines to our thighbones.

Without the psoas, whose main job is to bring the hip into flexion (i.e., thigh closer to belly), those big-ass butt muscles would make it impossible for us to use our arms the way we do now.

Imagine doing a backbend like I am in the photo, and trying to read this post. Or do anything at your computer.

Or drive.

Or eat.

Or walk.

That’s right, if you didn’t have a psoas (also known as a hip flexor) on each side, you wouldn’t be able to bend your leg up against gravity, and the action of your glutes, and take a step.

This shows up in yoga postures too, of course – a tight psoas would make bending backwards like I am doing in the photo really difficult.

Plus, if you couldn’t contract your psoas to lift your leg against gravity, how else would you do Utthita Hasta Padangustasana (aka Extended Hand to Big-Toe Pose)?

That, ladies and gentlemen, is the first reason I think the psoas is the most important postural muscle. There are others, involving magic links and its action on the spine. But opposing our glutes and keeping us upright? Pretty important.


Nadine Fawell teaches yoga, drinks coffee, and looks at too many cat pictures. You can find her at, on facebook and twitter.


  1. Reblogged this on Yoga with Nadine and commented:
    I’ve been reading Daily Cup of Yoga for YEARS. So I was rather delighted when I got a chance to do a guest post over there. On one of my favourite topics: the psoas. Say it with me So-Ass. Pop over and have a read!

  2. hahaha… So-Ass…. hahaha! [Easily amused today]. Brilliant post Nadine! I am always going on to my students about the psoas and getting blank looks – next time I will use this explanation! xx

  3. ahh! I love this article Nadine and have been curious about this muscle – I have a question I hope someone can perhaps answer! ..I have recently lost 20lbs due to stress and slightly underweight at 5 feet tall. Do you have any information on why this muscle has become so painful for me during yoga poses? I am very flexible and can get into the poses in your pictures easily. I used to be able to get into boat pose so quickly and legs straight out and now, the pain of my hip flexors makes it impossible. This all happened when I lost weight. Any ideas on weight loss and these muscles being strained or why they are so painful now? ( I have done yoga for 9 yrs with no issues until I lost weight ). I have asked my yoga instructors and they are at a loss – just mentioning I must be over stretching/ going in too deep..but this has been for months now since the weight loss.

    Thank you again!!

    1. Hi Wendy!

      What an interesting situation…
      I’d need to ask more questions: first, did the weight loss come along with a change in exercise patterns? Maybe more running or cycling, even walking? All of these activities tend to tighten the psoas considerably.

      Another possibility is that your posture has changed with the weight loss, maybe you are walking with less of a swayback for example, and that could also trigger a tightening of the psoas.

      Lastly, it might be an emotional reaction – when I lost weight, I felt very exposed, and I ended up tightening up my hips 🙂

      Have a think, email if you want more info.

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