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The Psoas is NOT a Hip Flexor


The Psoas is NOT a Hip Flexor

The psoas is not a hip flexor – okay, there I have said it! Usually I warm my students to this idea before I spring it on them. However, I guess I am feeling bold. Whether or not you agree with me that the psoas is something other then a flexor muscle, I invite you to test out my reasoning during your next practice.

The iliopsoas, fondly known as psoas (so-as), is the core muscle of the body and it is the only muscle to attach spine to leg. The psoas is formally categorized as a hip flexor. Flexors are defined as muscles that close a joint. Major flexors are located in the front of the body. Because the psoas moves from the deepest core at the 12th thoracic (or 1st lumbar) vertebrae diagonally forward through the front of the body and over the hip sockets and then back into the lesser trocanter of the femur, it is classified as a hip flexor. This is the biomechanical story, however, there is another story. This other story is embryonic; it is the story of how human life begins and develops in utero. It tells a story about an essential midline called the primitive streak from which everything emerges. Within this paradigm the psoas grows out of the human midline and is a messenger of the central nervous system; integral to primary reflexes, neurological proprioception, and personal integrity.

Even within the biomechanical model, it is worth noting that the psoas exerts an eccentric contraction, which is a confusing way of saying that the psoas doesn’t shorten. Rather it falls back along the spine while lifting the legs, bringing knee to chest, curling the spine, or bending at the hips. During walking, the psoas moves like a pendulum through the core maintaining its full length as the leg swings forward and back.

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The main reason why I believe redefining the psoas is so important is due to our behavior. If we think of this tissue as a muscle flexor then we will proceed in trying to stretch and strengthen it as we would any other flexor. However, if we think of the psoas primarily as neurological information, tender, supple, bio-intelligent tissue, we begin listening to it and recognizing it as a vital messenger. Although engaging the lower psoas as a flexor is definitely possible, doing so interferes with experiencing a deep, profound relaxation or neutrality within the core. Psoas muscles are not weak they are exhausted. Ultimately it is a responsive psoas that helps free the hip flexors to function with just the right amount of exertion.

Test out my reasoning by starting your practice with constructive rest. On your back, knees up, feet on the floor, (the width apart of your hip sockets). This rest position lets gravity release tension from your psoas. Roll to your side and get up slowly, take your time to sense the shifts and changes in weight through muscles, tendons and bones. Prepare for performing a runners lunge on the reformer. When ready, notice how simply imaging your psoas neutral, rather than engaged (in both your hips), allows a deeper relaxation, which enhances your sense of skeletal weight. There is a major artery (and vein) directly on top of the lower psoas, thus a deeper sensation of relaxation in the psoas allows for increased blood circulation within the hip socket, pelvis, and leg. Experiment in the same way while in the C curl. It does not matter what direction the spine is moving, the psoas is responsive tissue, branching out, and sending proprioceptive information. The spine or embryonic midline is always neutral – your core is the eye of the storm and your inner sanctuary does not react to every push or pull from external muscles, or life’s external demands for that matter.

It takes a quality of discernment to differentiate the psoas from the hip flexors. If the quads are over developed or the tendons of the hip flexors excessively tense, it is necessary to first soften. However once you do, I believe you will be amazed at what a paradigm shift can do to bring a deeper sense of and responsiveness from your sweet psoas.

For those who already sense their lower psoas soft and responsive, include your upper psoas by lifting one arm (on the same side as the straight thigh or in advanced lunges, the leg that is behind the pelvic basin), and place your hand on your head, turning slightly, look up towards your floating elbow. Psoas tissue moves spatially 360 degrees, but only when free to do so. Sensing your whole psoas spreading down towards the platform (earth) and freely up towards your heart (heaven) is simultaneously a feeling of fullness and emptiness. Experiencing complete core relaxation awakens a profound connection to breath and your heart’s desire.

The psoas is juicy, supple, and dynamic: a major player in full body orgasms. It is the filet mignon, the finest cut of meat humans eat in other animals. Chefs tell me the psoas tissue is a different color, texture, and quality from any other muscle meat. This gets me thinking that perhaps the psoas is more like the tongue, an organ of perception… maybe it isn’t even a muscle!

By · Posted on September 8, 2009 · Topic Feature Articles

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26 Responses to “The Psoas is NOT a Hip Flexor”

  1. Marguerite Ogle on September 8th, 2009 12:34 pm

    Beautifully said, Liz. The role of the psoas at the core of our body is amazing and you’ve brought much of the deeper meaning of the psoas into the light. Thank you.

  2. Lynda Lippin on October 25th, 2009 3:23 pm

    Thank you so much for this article! You have no idea how many guests I see here at Parrot Cay who are convinced that their psoas must be stronger or longer or something. People forget that there are other hip flexors and that the psoas attaches to the spine and should be treated with a bit more respect. I am working more and more on getting people to release into that hip socket and feel that lovely softness that can occur. I say it again, thanks!

  3. Babs King on January 15th, 2010 12:56 pm

    Thank you Liz for the explicit article! This helped me explain the psoas to several challenged clients.

  4. The Movement Studio Pilates » Blog Archive » Post-Olympics. And the psoas. on March 7th, 2010 10:42 pm

    […] article: “The Psoas in NOT a Hip Flexor” is interesting, and relates to a part of the body that Pilates focuses carefully on. Liz […]

  5. Andrea Cousins on March 24th, 2011 8:56 pm

    Enlightening and helpful. I plan to practice this myself in order to better relay this to clients.

  6. Pilates Person on June 13th, 2011 1:42 pm

    Fabulous article. Especially this: “perhaps the psoas is more like the tongue, an organ of perception” exactly how I work with my clients. Much more effective than forcing it. Thanks for the additional language. Can’t wait to tell my clients their psoas is like their tongue! :)

  7. Jana Cerny on June 13th, 2011 11:41 pm

    a beautiful, intelligent, thoughtful and engaging article. having been in one of Liz’s classes it was nice to touch in her approach again. i totally recommend studying with her if possible.

  8. Carrie Tyler on June 17th, 2011 5:58 pm

    Love this article. Absolutely perfect explanation of the psoas as something so much more than a hip flexor. The psoas is luscious!

  9. Dead Butt Syndrome | Pilates Digest on October 8th, 2011 11:12 pm

    […] to my hamstring injury, my iliopsoas on the right side tightened up, and became hypertonic. It always seemed to be in a shortened […]

  10. Daniel le Roux on December 2nd, 2011 6:07 am

    Wonderful article, thoroughly enjoyed it. Will pass it on to all our Tempo Pilates trainers. Thanks!

  11. patrick johnson on June 6th, 2012 1:12 pm

    Very silly article. Of course the psoas is a hip flexor. Imagery is fun and it is fun to think about embryos and stuff, but you make many factual mistakes in this article.

  12. Peggy Burgess on July 1st, 2012 2:31 am

    If the psoas is eccentric , which muscles are it’s concentric counterparts? I would suspect that it isn’t always in eccentric phase, what does it do when in extension?

  13. Peggy Burgess on July 3rd, 2012 7:18 pm

    In the Anatomy of Movement (page 62) Calais-Germain says that electromyographic recordings show, paradoxical results in moving subjects, showing that it acts as an erector along with the tranversospinalis muscles, stabilizing and holding spine erect. From my personal experience relaxed lengthening works very well on the psoas, better than tradition lunge position. I found the position in the article helpful, I’m not sure how it works.

  14. Erin Evans on July 20th, 2012 4:59 pm

    I found this article very interesting and it has definitely got me thinking about the psoas differently. I have just begun to study and explore the psoas in more depth.

    Patrick, please share, what are the factual mistakes in the article.

  15. jesper thirup hansen on December 9th, 2012 12:14 am

    The article has many mistakes. Your conclusion is based on your own philosophical reasoning and those mistakes. I’ll be happy to explain myself if there’s any interest. I’m sure the exercises are good. It angers me that people like you are trendsetters, because you’re just saying what ever you please.

  16. Jesper Hansen on December 15th, 2012 12:25 am

    The article has many factual mistakes. The conclusion is based on those mistakes and her own philosophical reasoning. I’ll be happy to explain myself if someone wishes. I’m sure the exercises are good. It angers me that people like her are trendsetters, because she’s just saying what she pleases.

  17. Sharon Hoge on March 21st, 2013 12:40 pm

    Hi, Just realized after FIVE years of pain like you can’t believe that I MUST have a very tight posoa. 2 surgeries. 3 chiropractors, PT with 3 places. TONS of $$$$ spent. Put my family through hell with me crying with pain and being miserable..Can anyone relate?? Now what do I do? It started with a faint deep ache in my hip, Now it aches my glute, IT band, low back and of coarse my hip. I also go to Pain management. Please help me. Everyone wants to sell me something. I am from Gibsonia Pa. 20 min north of Pittsburgh. Thank you SO much!!

  18. Chris Kinch on April 3rd, 2013 10:57 pm

    Liz I am thoroughly intrigued by the claim in this article and would greatly appreciate e reference to where you got this information.
    I am a student of osteopathy and have been practicing as a remedial therapist for years and I treat psoas on a regular basis and can physically palpate and feel psoas under tension during supine and standing hip flexion.

    Your response and reference source would be greatly appreciated.

    Kind regards,

    Chris Kinch

  19. Sheena Nadeau on January 28th, 2014 12:37 pm

    I’m sorry, you may discuss this as the “psoas paradox” however, the psoas and iliacus separately and work a bit differently due to their respective origins. biomechanically, this article is not based in facts. i hope this is not the same teaching in your books, including on scoliosis as this can damage your client.

  20. unwarranted on September 13th, 2014 4:55 am

    What a material of un-ambiguity and preserveness of valuable
    familiarity on the topic of unexpected emotions.

  21. Nikki Ralston on March 28th, 2015 4:59 am

    Liz your years of research has inspired me deeply. I resonate so deeply with everything you say from an embodied experience of suffering for years from Psoas dysfunction. As a yoga teacher and massage therapist your work has inspired a huge part of my journey, I have shifted so much in my body from understanding this muscle of perception more expansively and it has changed the way I teach for the better. Thanks to your work I am now able to help facilitate others to a deeper awareness. With gratitude.

  22. The psoas orgasm on March 28th, 2015 6:32 pm

    A great example of how anything can be said about anatomy, biomechanics, and embryology, altogether, with a complete lack of sound logic. As a biomechanics teacher in osteopathy and a pilates teacher, I think I will give this article as an example of how NOT to understand the motion and core of the body to my students. As a popular statement with no sound logic often taught in pilates, which states that your psoas is not solicited when well contracting your deep ab muscles while doing the “teaser”, claiming the psoas is not a hip flexor is the same. Considering movement with a holistic and global approach is very interesting but can lead to misleading claims.

  23. Mellisa Rupp on March 28th, 2015 10:43 pm

    I am not so sure I agree, ironically I just had a day of releasing psoas, iliopsoas and “secondary hip flexors.”
    You may want to check out the work of Pegg Lamb, MA, LMT, NCTMB.
    Also another great book to look into would be the vital psoas.

    After attending class and having the work done, today I am sore, mostly when seated and flexing my hips ie walking etc…

    While I appreciate your intelligence, you may need to rethink you thought process.


    Mellisa Rupp, LMT, MBLEx

  24. Nico Pauly on March 31st, 2015 1:38 am

    It is always wrong to discuss a muscle as an alone standing device. The psoas is at the time a spine stabilizer as a hip-pelvis movement muscle and as a glider for the kidneys.
    It has at least 4 but mostly 5 segmental origins from L1 to L5 that are important for lumbar stability and keeping up lumbar lordoses in an bilateral contraction state. These dorsal segmental parts are innervated by short spinal nerve endings.
    The long ventral muscle fibres, innervated by the femoral nerve, and connected to the iliacus muscle (ilio-psoas) are involved in movement of the hip and the pelvis while walkin, running and so on. Of course these ventral parts are hip flexors and hip exorotators.
    The kidneys are hanging with their fascal sac over the psoas muscle, uising it as a glider. The kidneys are attached to the diaphragm and, while breathing in and out, the move over the psoas muscle.
    The origins of the diaphragm are the same as from the psoas musle
    So, the psoas is a part of a whole integrated muscle-organ chain.

  25. jesper Hansen on October 16th, 2015 3:50 am

    I’m happy to see that more and more people are presenting some facts in the comments. I’m disturbed to see that the author has never responded to any of the comments.
    It’s nice that the author has taken the time to feel how she relates to her body and how it feels. it’s disturbing that she’s presenting her feelings as facts that other people then refer to as….facts.
    Does anyone else think that when she’s talking about upper and lower psoas, she might be talking about psoas and iliacus?

  26. Gail Rosenberg DC on December 3rd, 2015 12:47 am

    As a chiropractor, I regularly check the length of my patients’ psoas muscles. Often I find that both are shortened and tight from our sitting culture and usually one side is tighter than the other. I have a number of stretching maneuvers that I perform on my patients to remedies these problems once I have adjusted their spines. These stretches are very effective in lengthening the psoas and my patients experience immediate benefits in posture and mobility. There is no reason to believe that these muscles cannot be stretched.