Why Filet Mignon Is So Tender—and What That Tells Us About the Human Psoas
===
[00:00:00] Welcome to what I'm reading, what I'm thinking, where I share the research behind my upcoming book, and how it's shaping the way I think about fascia structure and movement. Let's dive in.
Let's start with something delicious, filet mignon. That buttery tender cut of steak that practically melts in your mouth. It comes from the PSOAS major of a cow. Yep. Filet mignon is the tenderloin. Anatomically, that's the same muscle that we humans have running from our lumbar spine down to our femur.
This deep, hidden, and surprisingly insightful muscle reveals so much about our own bodies. So why is filet mignon so tender? In cows, the PSOAS doesn't do much work. It's a deep postural muscle that doesn't deal with the weight bearing or locomotion demands that say the glutes or the quads handle.
Because of that, it doesn't build up dense connective tissue, doesn't get full of tough collagen cross-linking [00:01:00] and doesn't develop the kind of resilience we associate with more active muscles. It remains pristine, underused under, stressed, and therefore incredibly soft.
That's what makes filet mignon so prized. It's essentially unused muscle free of the wear and tear that toughens other cuts. This culinary fact offers a perfect metaphor for our understanding of our own anatomy. The human psoas is often lumped in with other hip flexors like the iliacus and the rectus femoris,
but the truth is it plays a much more nuanced and almost perceptive role. Yes, it can flex the hip, but it does that best when the spine is stabilized. Unlike the iliacs, which is anchored firmly to the pelvis and clearly built to lift the leg, the PSOAS spans multiple vertebra, crosses the pelvis and connects directly to the femur.
That unique positioning, deeply embedded within our core and [00:02:00] interwoven with a rich fascial network, gives it exceptional leverage and proprioceptive sensitivity. It's almost as if it's listening to the body's subtle shifts. I've come to think of the PSOAS as less of a prime mover and more of a sentient bridge, connecting trunk to legs, breath to spine, and postural tone, to pelvic rhythm.
It is not just a muscle, it's an integrator of systems, a central communicator within our fascial web. And that brings me to one of the more underappreciated relationships in the body. The synergy between the PSOAS and the Quadratus lumborum or QL. These two muscles work as deep diagonal stabilizers.
They're continuities, ensuring they communicate and coordinate effectively. Together. They orchestrate subtle shifts in pelvic spinal curvature and side to side movement. Imagine walking as one leg swings forward.
The opposite side of your pelvis needs to stabilize and slightly [00:03:00] lift. That pelvic lift that's often a QL. And PSOAS combo move, working alongside many other synergies to create what appears to be effortless movement, this partnership creates the foundation for efficient gait, a biomechanical dance we rarely consciously appreciate,
But here's where things get even more interesting, especially when we consider the ideas I explore in my upcoming book. When you zoom out and think in terms of pressure, especially the hydrostatic and pneumatic pressure systems within us, the PSOAS isn't just a stabilizer or mover.
It's a crucial pressure regulator. It's extensive fascial connections. It is critical role in spine pelvis orientation, even its intimate relationship with the diaphragm. All of these make it a key participant in how we balance internal pressure. The PSOAS through its tone and [00:04:00] its fascial scaffolding helps maintain the integrity of our core cylinder, influencing everything from spinal stability and breathing mechanics to visceral function and even fluid dynamics.
Which by the way, could explain why so many people are sensitive or guarded around their PSOAS. Does this resonate with your own experience of a tight or tender PSOAS? It's often not just tight from overuse. It's reacting to chronic postural stress, breath holding patterns, protective bracing,
and perhaps even stagnation within our fluid systems. When someone says they're PSOAS feels tight, I hear that as a signal of a deeper imbalance, perhaps a loss of adaptability in the core pressure system reflecting patterns of stress, trauma, or habitual tension held within the very fabric. So yes, the cows psoas is tender because it's not doing much an evolutionary quark that benefits our pallets.
The [00:05:00] human PSOAS though it might not be lifting heavy things or generating explosive power in the same way other muscles do, but it's doing something even more critical, helping us stay upright, breathe with depth, and move with fluid adaptable coordination. Our evolution as bipeds has transformed this muscle from a similar hip flexor into a sophisticated coordinator of movement, stability, and internal environment.
The very fact that we stand upright has given our psoas a role that the cow psoas never evolved to perform and understanding this evolutionary difference and the profound fascial intelligence it embodies helps us better appreciate its vital function in our own bodies.
That's it for today's dive into the research. If you're enjoying this process and want to see how all these ideas come together, make sure to subscribe and stay tuned for the next episode. There's a lot more coming as we explore the fascinating intersection of anatomy, evolution, fascia, and [00:06:00] movement.
