Rolling back onto your tailbone instead of sitting on your sit bones is the most common posture habit I see in the clinic, and one of the easiest to undo. When the tailbone curls under, the bottom of your pelvis closes and the pelvic floor muscles living there are held short for as long as you stay seated. Short is not the same as strong. Letting the tailbone lengthen back behind you takes that strain off, and it costs nothing but attention.

What “untucking your tailbone” actually means

Your tailbone is the coccyx, the small remnant of a tail, and it has one job. It opens or closes the bottom of your pelvis. Stand up tall and the coccyx points back and down, leaving that opening clear. Sit down and roll back onto the tailbone and it tucks underneath you, shortening the opening.

You do not have to look far to see why it happens. Sofas, car seats, office chairs and dining chairs all invite you to sink in low and let the spine slump. That slump is the same thing as a pelvic bowl tipped backwards with the tailbone tucked under. We were never built to sit this much, and our furniture was never built to keep us out of the tuck.

Why a tucked tailbone matters for your pelvic floor

The pelvic floor is a sling of muscle running from your pubic bone at the front of the pelvis to your tailbone at the back. Bring those two ends closer together and the whole sling sits shorter than it wants to.

Held short day in and day out, the muscle gets tight. Tight sounds like it should mean strong, and it does not. A pelvic floor that never lengthens cannot contract efficiently when you actually ask it to, which is the opposite of what most people assume. Over time that shows up as leaking when you laugh or run, a heaviness or dragging feeling, pain during sex, or a dull ache low in the pelvis.

There is a knock-on effect further up as well. The pelvic floor is part of the deep core system that holds your spine and pelvis steady. When it is gripping, that system loses some of its ability to do its job, and the back takes more of the load than it should.

Ageing, menopause, pregnancy and childbirth all get blamed for pelvic floor trouble, and they do play a part. But a lifetime of sitting in a tucked pelvis does a quiet amount of damage on its own, and that part is entirely fixable.

How to sit with your tailbone untucked

Stand more than you sit

Take every chance to stand that the day offers. A standing desk, a phone call on your feet, a meeting that happens while walking. Standing is the position your pelvis was designed for, and every minute of it undoes a minute of sitting.

Choose a firmer seat

When you do sit, pick the chair that holds you up rather than swallowing you. A seat you sink into encourages exactly the slump described above. Firmer, with your hips slightly higher than your knees, keeps the pelvis level and the tailbone free to lengthen.

Sit on your sit bones

Feel for the two bony points at the base of your pelvis. Those are your sit bones, and they are what you are meant to sit on. Rock gently forward and back a few times and you will feel yourself tip onto the tailbone and then come back onto the sit bones. Aim to live towards the front end of that range, with your weight resting over the sit bones. That is the level pelvic foundation position.

Let the pelvic floor release

This is the part people find hardest, because it means doing less rather than more. A tense muscle is not a strong muscle. You would not walk around with your shoulders up by your ears all day, and the pelvic floor deserves the same release. Stop gripping it. Let it lengthen and soften the way it does when you are drifting off to sleep.

Squat rather than bend

When something ends up on the floor, squat to it instead of folding at the hips. Squatting asks the pelvis and legs to work through a full range, which keeps everything mobile and stops the same short patterns setting in.

Vary how you move

Do not spend eight hours in one posture and then wonder why your back complains. Change position often, and change what you do. Repetition in one shape is what causes trouble, not any single shape on its own.

The take-home message

Simple daily changes add up to a lasting difference in pelvic health. Stand when you can. Choose the better chair. Sit on your sit bones rather than your tailbone. Let the pelvic floor release instead of gripping it. Squat, move, and vary the way you move.

None of this is about sitting perfectly. It is about noticing when you have rolled back onto your tailbone, and coming back to the sit bones. Do that a hundred times a day and your pelvic floor gets the length it needs to work properly.

Ready to put an untucked pelvis into practice? Our Pilates Fundamentals tutorials teach spinal neutral and the deep postural muscles that hold it. If you would rather be checked in person, our clinical Pilates classes in the Sydney CBD studio work the same positions with a physio watching.