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Your Core Canister

This is the fifth post (Week 14) in the series "What you don't expect when you're expecting".

Your core canister.

It goes through quite a bit of changes during pregnancy, most obvious being the growth of a tiny human within it. Many pregnancy related aches and pains are the result of something going on with your core canister, causing it to not function at its best.

But before getting into those “what ifs,” it's important to understand what your core canister is and why it’s so important that it operates efficiently during pregnancy.

Why? Let me count the ways:

  • It helps you transfer force from one area of your body to another

  • It helps you keep you balance

  • Improved posture

  • Less risk of pelvic floor issues or diastasis

  • Better breathing which leads to increased stamina

  • More efficient pushing

  • Flatter tummy (I know we’re not supposed to care about such things, but it is a side effect!)

  • Decrease chances of low back pain

Whooooo - sign - me - up!

Quick note:

This post is far from being completely comprehensive - there is just way too much information about all these parts and pieces out there. The purpose of this post is to get you acquainted with the pieces of the puzzle, so you have a better idea how to handle any issues that may come your way.

So let’s meet the parts of your core canister.

1. Diaphragm

Your diaphragm makes up the top of your core canister and its number 1 job is making sure you breath. It’s a striated muscle, and just like any other striated muscle, it can get stronger. When you inhale, the diaphragm contracts and descends - it actually gets flatter. When you exhale, it relaxes, ascends, and regains its dome shape.

The diaphragm originates from the inner surface of your lower 6 ribs, the upper 2 or 3 lumbar vertebrae, and the inner part of your xiphoid process (the lower tip of your breastbone). It inserts into the central tendon of the diaphragm (essentially in the middle of itself).

The diaphragm also has fascial connections to many muscles including your transverse abdominals, quadratus lumborum, and psoas major.

Because of all these connections, your bone placement, aka posture, can have a large effect on your breathing abilities.

2. Pelvic Floor

This is the bottom of your canister. We celebrated the pelvic floor last week so if you need a refresher on how to voluntarily contract and release those muscles, go have a reread.

So when you inhale and your diaphragm descends, it pushes into all the stuff contained within your abdominal cavity - stomach, intestines, uterus, bladder, and a whole host of other organs. When you are in a relaxed state, other parts of your core canister also move in response so that nothing inside gets smushed.

A fancy way to say this is, you maintain a near constant intra-abdominal pressure (IAP).

Specifically, your pelvic floor moves in parallel with your diaphragm - descends on an inhale and ascends on an exhale. It just does this. You shouldn’t have to think about it.

And this right here is why the release/relax component of pelvic floor training is so important. Think of it like a trampoline. It stretches so it doesn’t rip. Now, a hypertonic (too tight) pelvic floor will have trouble descending on the inhale. While your pelvic floor won’t rip like a trampoline, what could happen is some leaking, or urinary stress incontinence.

I’ll get into the mechanics of “Peezing” in a few weeks.

3. Transverse Abdominals

This is the cylinder part of your core canister, wrapping around the outside. Just like your pelvic floor, your belly should also move out on the inhale, and recover on the exhale. It also just does this.

The purpose of your TvA is to compress your abdominal contents (maintaining that IAP) and forced exhalation. It’s your internal corset responsible for stabilizing essentially your entire body.

Those other abdominal muscles? They’re mostly for show.

The TvA wraps horizontally around your midsection. It originates from the iliac crest, inner surface of your lower 6 ribs (just like the diaphragm!), and your thoracolumbar fascia. It inserts into the linea alba via the rectus sheath.

The linea alba is the “white line” in between the six pack muscles that can be seen in anatomy illustrations. It’s an important fascial connection during pregnancy that I’ll get into more next week.

Finding your TvA and consciously contracting it can be challenging. I’ve included a breathing exercise at the end of this.

4. Multifidus

Finally, in the back you have your multifidus. These are the most important spinal stabilizers you’ve got.

They run the length of your entire spine, but mostly I want to focus on the lumbar ones. They originate on the sides of a vertebrae and then travel up and in (diagonally) to insert into another vertebrae 2-5 above the origin.

They assist in spinal extension (bilateral contraction), side bending (ipsilateral contraction), and rotation (contralateral contraction).

Think of the multifidus as the anchor point which allows all the other parts of your core canister to move.

They can be difficult to voluntarily contract because they are so small, your brain may have trouble “attaching” to it. Bird-Dogs are are great exercise to strengthen them IF you aren’t letting your low back move around when performing them. Remember, they are spinal stabilizers.

Bringing it all together:

If you haven’t noticed by now, all components of your core canister share one very important function…


Breathing is literally the best exercise for your core canister, specifically 360 degree breathing.

Here is a great breathing exercise. I encourage you to try it with a Theraband wrapped around your ribs to have something tactile to breath into.

A Breathing Exercise

Lie on the floor. Face the ceiling and bend your knees. Heels in line with sitz bones, feet flat, pelvis neutral. Honor the natural curves in your spine.

Place one hand on your belly and one on your chest. Observe your breath without judgement. Are you a chest breather? See if you can bring it down to your belly.

Allow your belly to become round with inhalation; your diaphragm moves down and becomes flat. Relax and allow yourself to exhale; your diaphragm moves back up into its dome shape.

Add your pelvic floor into the mix.

Inhale and try to relax your pelvic floor as your diaphragm goes down and your belly expands. As you exhale, imagine the space between your ischial tuberosities narrowing, as your belly pulls inward and your diaphragm returns to its dome shape.

Repeat, exhaling a bit more forcefully each time;

10 birthday candles, 20 birthday candles, 50 birthday candles, 100 birthday candles

Now add some accessory muscles.

Put your thumb at the bottom of your ribcage and fingers over your belly. Inhale and expand your ribs as much as possible.

During your exhale, feel the ribs go down.

Repeat, increase the forceful exhalation each time. 10, 20, 50, 100 candles...

Keep the PF / TvA / Diaphragm timing. Be mindful not to bear down.

Now let’s try breathing into the posterior ribs.

Sit tall. Inhale as you lift your arms, exhale as your arms lower. Coordinate this with your waist getting smaller (TA contraction) as you lower your arms. Continue to imagine your PF lifting upwards as you accentuate exhalation.

Gradually increase the intensity. 10, 20, 50, 100 candles...

This TvA breath activation has a bunch of names but when pregnant, I particularly love “Hug the Baby / Free the Baby” courtesy of Pregnancy Pilates Impact. On the exhale, use your TvA hug the baby with your belly, and on the inhale, release.

Let me know how finding these muscles goes. This breathing technique is your best insurance against those pregnancy related woes!

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