What Is IAP And How It’s Related To Core Stability

by | Nov 1, 2023 | Blog

If you’ve been around fitness for any given time, you’ve definitely heard about core stability, and you probably were told often that you need to “brace your core” or “activate your core”.

If you’ve been in the lifting world, you’ve probably gone a step further and been told or read about the importance of “bracing” your core like someone is punching you in the gut. Maybe you even have a lifting belt to help cue you to do this.

And if you’ve entered into the movement world, you may have heard about core stability being connected to IAP and your breath.

Or perhaps you’ve been (incorrectly) told the way to create core stability is through TA (transversus abdominis) ‘activation’ and drawing your belly button to your spine (spoiler alert: this actually DECREASES IAP and core stability!).

Whatever your background is that led you here, you’re reading this because you have questions, and the purpose of this blog is to answer those questions.

What is IAP?

Intra Abdominal pressure (IAP) refers to the pressure in the abdominal cavity that changes with changes to the volume of your abdominal cavity or the contents inside of it.

Your abdominal cavity is made up of the abdominal wall (including your abdominal muscles, fascia, etc.), the diaphragm (ceiling), and the pelvic floor (bottom).

While this cavity does contain organs, the dynamic pressure generated from the contraction of the diaphragm and additional surrounding muscles also serves an important function- core stability.

How does the diaphragm create IAP?

When your diaphragm contracts, it descends and decreases the volume of your abdominal cavity. As a result, the pressure in the cavity increases (yay for physics!).

Your diaphragm contracts every time you inhale, to pull air into your lungs. And when it’s functioning optimally, it is also creating a slight increase in the pressure in your abdominal cavity. This means that every single breath is an opportunity to create a small amount of IAP or core stability which is super cool!

Your diaphragm also contracts when you need to create core stability, which is any time you move a part of your body. And this can happen independently of your breath, too!

The pressure changes from your diaphragm contracting can be minimal (like a simple breath) or more significant (like when you lift a heavy weight off the ground).

The additional increase in pressure occurs when the additional muscles (your obliques, back muscles, pelvic floor, rectus abdominis and transversus abdominis), also generate force by eccentrically contracting, creating a more rigid abdominal wall. (An eccentric contraction is one where a muscle is lengthening but still creating force.)

This is what happens when we use our breath to “brace” when we are lifting heavy weights, and this is why you may have heard things about making sure your breath is distributed 360*, or all around your abdominal cavity.

Core stability, or IAP, is created by a system of muscles working all together.

Why does this all matter?

First and foremost, understanding how to use your breath to generate IAP can help you tap into more of your strength and break through plateaus in the gym!

But also, like many other systems in our bodies, parts of the system can start functioning less optimally and contribute to health issues, pain, injuries, etc. Regulating IAP is no different.

Many people struggle with an altered breathing pattern, which you can read more about in this blog post. Or they have postural changes due to a lack of movement variability, sedentariness, etc.. And after years or decades, this can contribute to a loss of strength and endurance in the muscles that regulate IAP, therefore resulting in a loss of the ability to create the amount of core stability needed for lifting heavier weights or even just daily activities.

Think of the pressure generated like a coke or soda can, before you open it and release the pressure. As you try to squeeze it, it’s really tough to dent or break due to the pressure within the can, similar to the pressure created in your abdominal cavity. You can stack alot of weight (which is a compressive force) on top of it with no problem).

However, once the can has been opened or dented in from a slight loss of pressure, it’s much more soft and easy to dent or squeeze and change the shape of. It’s unable to withstand as much force- especially compressive force. If you try to step on it, it crumbles.

While our bodies aren’t quite that fragile & we can withstand a lot and still function because they are great at adapting & compensating.

Over time, this can contribute to a lot of different musculoskeletal issues.

The loss of IAP strength has been attributed to many different issues such as: low back pain, SI joint pain, pelvic pain, hip pain, diastasis recti, hernias, shoulder pain, neck pain, leaking, and more. Not to mention it can often cause a plateau in strength or performance gains.

Generating IAP functions not just as assistance to tap into deeper levels of strength but also provides additional support for our spines. Especially when we are lifting heavy loads that add a compressive load to our bodies.

This is why Incorporating a breathwork practice and learning how to use your diaphragm to create more optimal IAP can truly be life-changing.

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A photo of Dr. Jen Hosler standing with a barbell instructing the deadlift.

Hi, I'm Dr. Jen Hosler.

I’m a bookworm, science nerd, and coach of all things movement (physical therapist and strength & mobility coach). You can catch me sleeping in & having a slow morning, doing CARs & lifting heavy things, or sipping a glass of wine on my time off.

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