Forgotten Muscles #1: The Pelvic Floor, a Hidden Pillar of Movement and Posture

We know its name, we think we know where it is, we've vaguely heard about its role in breathing or core stability… but let’s be honest: if I gave you a piece of paper and a pencil, could you really draw your perineum?

Probably not — and that’s precisely where the story of this deep muscle, as essential as it is discreet, begins.

In our series on forgotten muscles, the pelvic floor holds a prominent place. Invisible, rarely mentioned, sometimes taboo, it accumulates all the ingredients that allow a muscle to remain largely underestimated. Yet, its fibers work with every movement, every exhalation, every change in posture… without you even realizing it.

This first article has a simple goal: to shed light on a muscle group that most people think they know, but very few truly understand its anatomy, muscle layers, fiber orientations, and key roles. Before discussing coordination, breathing, or athletic performance (which will be the subject of subsequent articles), let’s take a moment to understand what lies behind this "muscular hammock" that your body activates hundreds of times a day.

If I asked you to draw your heart, your biceps, or even your diaphragm, you could probably manage it. But your perineum? Crickets.

And it's not a criticism: no one can truly represent it without a model. It’s perhaps the only structure in the body whose name we know… without having any precise mental image.

Why?
Because the perineum lives in the shadows.
Hidden, deep, discreet. An "invisible muscle" that we nevertheless mobilize dozens of times per minute, simply by breathing, moving, changing posture, laughing, coughing.

That's why, since we can't visualize it clearly, the brain doesn't attribute any functional existence to it.
This is the paradox of deep muscles: they work constantly, but they are almost never part of our conscious body map. The result: we ignore their importance… until something goes wrong.

Before going further, let's pause for a moment on this simple observation:

How can an indispensable muscle be almost absent from our body schema?

The perineum is one of those discreet muscles that we constantly engage, but hardly ever perceive. 

The perineum is often described as an intimate, discreet muscle, but rarely as a player in movement and stability. Yet, its links with breathing, posture, and the lumbar spine are deep and constantly engaged in daily life.
The perineum-posture forms an essential biomechanical pair for stabilizing the entire lumbopelvic region.

The perineum is neither visible, nor palpable, nor spontaneously associated with performance.

Unlike superficial muscles — quadriceps, abdominals, biceps — it does not produce "spectacular" movement and is never highlighted in conventional training.

Without visual representation, it remains absent from the body schema, making it difficult to consciously control.

The perineum is located in a region of the body rarely discussed in social or athletic contexts.

This intimate dimension contributes to a deficit in bodily education: it is not talked about, we are not taught to feel it, we often ignore how it works.

As a result: we tend to only pay attention to it when a problem arises, whereas understanding it should be part of the basics of human movement.

For a long time, the perineum has been associated almost exclusively with female health.

This idea stems from a real anatomical fact: in women, the pelvic floor has three orifices (urethra, vagina, anus), which creates a wider central opening than in men.

In men, the structure is more "closed," with only two orifices.

However, this anatomical difference does not change the fundamental function of the pelvic floor:
in men as well as in women, it contributes to stability, pressure regulation, breathing, and posture.

Thus, reducing the perineum to a "female muscle" masks its essential role in human movement, regardless of sex.

Unlike superficial muscles, the perineum works subtly, with contractions that are often reflexive, automatic, and coordinated with breathing.

Its function does not rely on brute force, but on precise timing: activation, relaxation, modulation.

Because its actions are barely perceptible and rarely explained in traditional training, it remains a "blind spot" in the understanding of movement.

Now that we know why this muscle is so misunderstood, it's time to open the blueprint and observe what truly lies beneath our pelvis.

If the perineum remains difficult to visualize, it's also because its structure is much more subtle than a simple "muscle at the bottom of the pelvis."

The pelvic floor is a true architectural ensemble, made of several muscle layers that interlock and crisscross, much like a system of internal beams that support and stabilize the entire pelvis.

Unlike superficial muscles, whose fibers are broad, visible, and easy to locate, the pelvic floor muscles are deep, delicate, and oriented in multiple directions. This multi-fasciculated organization allows it to perform very different tasks: supporting organs, absorbing pressure variations, adapting to breathing, and stabilizing posture.

To better understand this complex, it is useful to distinguish two levels: the pelvic floor in depth, and the perineum region superficially. This nuance clarifies many common misunderstandings.

The pelvic floor is often described as a "hammock," but this image, however convenient, oversimplifies a richer reality.

It is actually composed of three main layers:

• a superficial layer, in contact with the outside, involved in the sphincters and immediate perineal function;
  
  

• an intermediate, more tonic and stabilizing layer;
  
  

• a deep layer, the pelvic diaphragm, dominated by the muscles of the levator ani (pubococcygeus, puborectalis, iliococcygeus).
  

These layers are oriented differently: some fibers pull forward, others backward, and still others upward.
This complexity is exactly what makes the perineum versatile and reactive, but also difficult to visualize mentally.

The perineum is not just a "muscle in the lower pelvis."

It is a deep structure that is involved in several essential functions: internal support, continence, respiration, and trunk stability.

Understanding these roles makes it clear why an invisible muscle can influence so many everyday movements.

The perineum helps keep pelvic organs in place — bladder, rectum, uterus, or prostate depending on sex.
It acts as an internal base capable of absorbing pressure variations when walking, laughing, or making sudden movements.
Well-coordinated support prevents sensations of heaviness or abdominal instability.

Continence is not based on maximum strength, but on the perineum's ability to contract and relax at the right time.

This system responds to very rapid pressure variations: laughter, coughing, jumping, change of posture.

When this mechanism becomes unbalanced, it is not necessarily a lack of strength — but often a lack of adaptation, a poorly synchronized activation with the rest of the trunk.

With each breath, the perineum synchronizes with the diaphragm.

When the diaphragm descends during inspiration, the pelvic floor muscles adapt to the increased pressure; during expiration, they rise slightly and participate in internal regulation.

This coordination has been described in several reference studies, notably "Activation of the human diaphragm during a repetitive postural task" (Hodges & Gandevia, 2000).

The perineum works in synergy with the transversus abdominis, lumbar multifidus, and diaphragm.
Together, they contribute to intra-abdominal pressure, which protects the spine and optimizes force transmission.

A coordinated perineum improves the efficiency of athletic movements, whether running, lifting, striking, jumping, or simply standing without compensation.

We don't see it, we don't know how to draw it, we barely ever talk about it…
And yet, this discreet little muscle group works tirelessly in the background every time you breathe, move, laugh, carry something, or simply stand upright without collapsing like a house of cards.

The perineum is somewhat the stage manager of the show: it doesn't appear on stage, but without it, nothing runs smoothly.
It supports, stabilizes, adjusts, compensates, and accompanies — all without seeking any glory.

So, you've just brought back into the center of your body awareness a muscle that your brain had filed somewhere between "I vaguely know where it is" and "oh right, is that useful?".
Good news: now you know it does much more than it's given credit for.

And the best part?
We've only explored one facet of its role.
Because behind this forgotten muscle lies a whole world of coordination, breathing, internal pressure, balance, and subtle nuances.

But that… is another story.

1. Rodrigues-de-Souza, I. et al. (2023).
   Between-sexes differences in lumbopelvic muscle mechanical properties of non-climacteric adults: a cross-sectional design.

   Nature.
   

2. Garzón-Alfaro, C. & Hall, T. (2024).
   Muscle Mechanical Properties of Pelvic Floor and Lumbopelvic Muscles in Women.
   Brazilian Journal of Physical Therapy.
   
   

3. Hodges, P. & Gandevia, S. (2000).
   Activation of the Human Diaphragm During a Repetitive Postural Task.
   Journal of Physiology.
   
   

4. Wallman, C. & Hall, T. (2022).
   Evidence for Increased Tone or Overactivity of Pelvic Floor Muscles in Pelvic Health Conditions.

   American Journal of Obstetrics and Gynecology (AJOG).