Is Your Psoas Locked? The Stress Muscle Hiding in Your Hips, and a Floor Test That Tells You
There is a deep core muscle wired into your breath and your fight-or-flight response, and it can brace for so long it forgets how to let go. Here is a simple test on your living-room floor that shows you whether yours has.
There is a muscle buried deep in your core, threaded along your lower spine and tucked beneath your organs, that has been quietly bracing every time you felt stressed, rushed, or unsafe. It is called the psoas, and if it has been holding that bracing pattern for months or years, there is a simple test you can do on your living-room floor in the next five minutes that will show you.
You have probably heard the phrase "we store stress in our hips." It gets repeated in yoga classes and on social media until it sounds like a slogan. But underneath the slogan there is real anatomy, and the psoas sits right at the centre of it. Once you understand what this muscle actually does, the slogan stops sounding mystical and starts sounding like a description of your own body.
Meet the only muscle that links your legs to your spine
The psoas major runs from the sides of your lower spine, the lumbar vertebrae, down through the bowl of your pelvis, and attaches to the inside of your thigh bone. It is the deepest of your hip flexors and one of the main muscles that lifts your knee toward your chest. It also helps stabilise your lower back. Anatomically it is the only muscle that connects your spine to your legs, which makes it a kind of structural hinge between your upper and lower body.
Here is the detail that matters for stress. The psoas anchors onto the same upper lumbar vertebrae that the diaphragm, your main breathing muscle, also reaches down to. The diaphragm has a fibrous arch, the medial arcuate ligament, that passes directly over the top of the psoas. So your breathing muscle and your deepest hip flexor are next-door neighbours, sharing real estate on your lower spine, and the diaphragm itself has fascial and neural links that thread throughout the body. When your breath gets shallow and high in the chest, the territory the psoas lives in changes with it. Breath and psoas are not separate stories.
Why a hip flexor became a stress muscle
Think about what your body does when it is startled or afraid. You curl. The knees draw up, the front of the body shortens, the spine flexes forward into a protective ball. That curling is, in large part, the psoas firing. It is part of the oldest protective reflex you own, the same flinch that pulls a foetus into a curl and pulls you into one when something slams behind you.
The trouble is that modern stress rarely ends with a clear all-clear signal. You are not sprinting from a predator and then resting. You are sitting at a desk with your hips already folded, your shoulders tight, a low hum of worry running all day. Muscles respond to sustained mental stress by quietly ramping up their activity. When researchers measured muscle activity during mental stress, everyone tested showed a rise in tension, not just people with a pain condition. Now picture that low-grade bracing held in a muscle that is already shortened by hours of sitting, in a muscle wired into your protective reflex. It learns the brace as its new normal. It stops fully letting go.
A short, guarded psoas is not damage. It is a muscle that has been doing its protective job so loyally, for so long, that it has forgotten it is allowed to rest.
This is also why deep hip openers can bring up so much. People sometimes shake, feel a wave of emotion, or unexpectedly cry when a long-held hip finally releases. It is not magic and it does not mean you are broken. When a guarding pattern that has been held for a long time starts to unwind, the nervous system shifts gear, and the body can discharge some of that held activation. There is an emerging area of work built entirely around this, sometimes called neurogenic tremor or TRE, where gentle shaking is used as a way to let the body unwind. It is worth being honest here. The research is still early and small, and in at least one careful trial the tremor exercises helped people but no more than simply meeting and talking did. So treat the shaking as an interesting, plausible release mechanism, not a proven cure. Your body knowing how to tremble out tension is real. The marketing around it sometimes runs ahead of the evidence.
The test: is your psoas actually locked?
You do not need a practitioner to get a first read on this. There is a well-established clinical test for hip-flexor length called the modified Thomas test, and a simplified version of it is something you can do safely at home. In people with low back pain it has been shown to give reliable, repeatable results when done with care. Here is a gentle home version.
Try this now
Sit on the very edge of a sturdy bed or firm bench, close to one end. Lie back, and as you do, hug both knees in to your chest so your lower back rolls onto the surface and settles flat. Hold one knee firmly into your chest with your hands. This locks your pelvis and protects your lower back, so do not let it go.
Now slowly let the other leg lower down toward the floor, letting it hang off the edge of the bed. Keep the held knee hugged in and your lower back flat the whole time. Let the lowering leg be heavy and relaxed. Do not push it down. Just let it drop as far as it naturally goes, and notice.
Look at three things. First, does the back of that lowered thigh come down to roughly level with the surface, parallel to the floor, or does it float up higher, hovering above the level of the bed? Second, does the lower part of that leg, the shin, hang loosely down, or does the knee want to straighten out to the front? Third, can you keep your lower back flat and the other knee hugged in, or does your back start to arch and your held knee get tugged away from your chest?
A thigh that rests down comfortably, with the knee softly bent and your back staying flat, suggests your hip flexors have room to lengthen. A thigh that floats up, a knee that pulls straight, or a back that arches to compensate are all signs of a short, guarded psoas and hip flexor on that side. Test both sides. They are often different.
Safety first. This is a gentle observation, not a stretch to force. If you feel any sharp pain, pinching in the hip, or strain in your lower back, come out of it and stop. Move slowly getting up. If you are pregnant, have had a hip or back injury, or anything feels wrong, skip this and work with someone in person instead.
If you want a second, even softer read, try constructive rest. Lie on your back on the floor with your knees bent and feet flat, about hip-width apart, and simply breathe for a couple of minutes. Rest your hands on the front of your hip creases. Can you feel the front of the hips and the deep belly soften as you exhale, or does that area stay gripped and busy no matter how long you lie there? Sometimes, as things start to let go, you may notice a faint involuntary tremble in the legs. That is not a fault. That is the beginning of release.
If you "failed", read this part slowly
A floating thigh is not a verdict. It is a guarding pattern, and guarding patterns are learned, which means they can be unlearned. The psoas is not torn or broken. It has simply been bracing so faithfully, for so long, that letting go no longer feels like an option to it. That is a nervous-system habit, and the nervous system is changeable.
The reason the psoas matters so much for how you feel is that it sits on the same lumbar vertebrae as your diaphragm, inside the same protective reflex as your stress response. So the way back in is rarely brute-force stretching. It is the slower, kinder work of teaching the muscle, and the system around it, that it is safe to soften. Breath is a big part of that, because slow breathing reliably nudges you out of fight-or-flight and toward rest, raising the calming, parasympathetic side of your nervous system and easing anxiety. When you change your breath, you change the environment the psoas lives in. If you would like the deeper anatomy and the myths worth retiring, Dana has written a companion piece, The Psoas, Reconsidered.
Here is the hopeful part. A body that has been bracing has not lost the ability to let go. It has just lost the practice. With the right kind of attention, breath, gentle release, and a nervous system that finally gets the all-clear, the front of your hips can learn to soften again, and a great deal of the tension you have been carrying as "just how I am" can start to ease. If your psoas test surprised you, that is the perfect place to begin. Dana's free guide, Why Your Body Won't Switch Off, walks you gently through exactly why your body stays stuck in high alert and the first simple practices to help it stand down. Download it, find a quiet patch of floor, and give your psoas the one thing it has been waiting for. Permission to let go.
Sources
- Bordoni, B. and Varacallo, M. (2024). Anatomy, Bony Pelvis and Lower Limb: Iliopsoas Muscle. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK531508/
- Park, R.J., Tsao, H., Claus, A., Cresswell, A.G. and Hodges, P.W. (2013). Changes in regional activity of the psoas major and quadratus lumborum with voluntary trunk and hip tasks and different spinal curvatures in sitting. Journal of Orthopaedic and Sports Physical Therapy, 43(2), 74-82. https://doi.org/10.2519/jospt.2013.4292
- Bordoni, B. and Zanier, E. (2013). Anatomic connections of the diaphragm: influence of respiration on the body system. Journal of Multidisciplinary Healthcare, 6, 281-291. https://doi.org/10.2147/JMDH.S45443
- Eimiller, K., Licata, A., Bilotta, A., Meagher, G. and Lahr, S. (2025). Reliability of the modified Thomas test in those with low back pain. Journal of Bodywork and Movement Therapies, 46, 134-138. https://doi.org/10.1016/j.jbmt.2025.10.038
- Luedtke, K., Mehnert, J. and May, A. (2018). Altered muscle activity during rest and during mental or physical activity is not a trait symptom of migraine: a neck muscle EMG study. The Journal of Headache and Pain, 19(1), 26. https://doi.org/10.1186/s10194-018-0851-5
- Zaccaro, A., Piarulli, A., Laurino, M., Garbella, E., Menicucci, D., Neri, B. and Gemignani, A. (2018). How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 12, 353. https://doi.org/10.3389/fnhum.2018.00353
- Harrison, E.G., Keating, J.L. and Morgan, P. (2018). Novel exercises for restless legs syndrome: a randomized, controlled trial. Journal of the American Board of Family Medicine, 31(5), 783-794. https://doi.org/10.3122/jabfm.2018.05.180065
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