While all Postural Restoration Insitute exercises are organized in their manuals around the muscle they are primarily designed to turn on, or facilitate, it’s also true that all PRI exercises serve multiple functions.

Remember that the goal of PRI is to turn off, or inhibit, overactive chains of muscles that are holding us in patterns. These patterns restrict movement, primarily in the frontal (shifting side to side) and transverse (rotation) plane. When you can’t move in these planes, bad things happen.

You become “extended”: increased curve in the lower back, flat mid-upper back, forward head posture.

In the typical pattern, we have the left AIC muscles, primarily the psoas, that are holding us in the left AIC pattern which consists of a left ilium rotated anteriorly and thus orienting our entire pelvis to the right and shifting our weight over the right foot.

We have the right BC muscles holding our torso, from just above the diaphragm (thoracic vertabrae 8), in a state of left counter-rotation, in an attempt to balance ourselves and maintain a straight line of sight.

Pelvis and ribcage repositioning serves to inhibit the overactive left AIC and right BC chains and thus gives us the potential to move our pelvis, ribcage and appendages through three planes of motion.

It enables to regain our lost frontal and transverse planes.

Repositioning puts our bones in a better postion so that we can now train the frontal and transverse movements that we had previously lost due to the position of an anteriorly rotated left ilium and counter-rotated rib cage.

Left Sidelying Right Glute Max

The Left Sidelying Right Glute Max looks like a clamshell. And it is–if that’s the label you choose for it.

But to a PRI minded person it is an exercise that trains the frontal and transverse movements of the right leg that we lose due to the left AIC pattern. It trains the ability of the right leg to abduct and externally rotate by using the right glute max and medius to do it.

Importantly, we are not trying to activate the meaty part of the right glute max that is responsible for pushing us forward.

We are attempting to activate the fibers of the right glute max that perform external rotation. These fibers are located in the posterior hip area and attach obliquely to the femur.

Here is a video I made for a client that shows the exercise.


A very important thing to realize is that this Left Sidelying Right Glute Max does a lot more that just activate the right glute max.

Here are a few more things it does:

1. Inhibits the right lat and right QL which are often overactive in the left AIC pattern. It can also help calm an overactive right psoas (which sometimes occurs). Frontal and transverse plane.

2. Opens up the right ab wall and right intercostals which are usually tight. Frontal plane.

3. Puts the left ab wall in a position that will facilitate the left internal obliques and transverse abdominis whose activity are required to establish and strengthen the left ZOA. Frontal plane.

4. Inhibits lumbar extensors via spinal flexion. Sagittal plane.

5. Facilitates right rectus femoris and sartorius, the two muscles we look to activate to get the right ilium forward. Sagittal plane. Facilitates the right glute medius and minimus. Frontal plane and transverse planes.

6. Inhibits the left psoas via the 90/90 position and via facilitating the right AIC chain. Sagittal plane.

7. Inhibits the right adductor magnus. Frontal plane.

With just a few tweaks you could add right low trap and tricep activation, left adductor faciliation, and right torso rotation into the mix.

PRI Exercises Do More Than Meets The Eye

The take home message in all this is that PRI exercises do a lot!

If you are a trainer, your mind probably thinks primarily about muscle facilitation and sagittal plane movement.

With each exercise you concentrate on what muscle should be working and probably think about sagittal movements (front to back) because that’s where most of our strength training is found.

But in reality, as PRI stresses, we are “sagittal animals” and facilitation minded to a fault. Anyone can turn on a left hamstring in the sagittal plane. Just have your client do a single leg RDL or hamstring curl.

The question is: can you turn off a left psoas, or turn off a right lat that is restricting frontal and transverse plane movements, at the same time you are turning on that left hamstring?

Remember, if you can’t inhibit an overactive chain of muscles, you can’t reposition a pelvis.

You also can’t move and breathe without compensation!

So if something like a Supine 90/90 isn’t working, it’s more likely an issue with not turning of the left AIC rather than not turning on the left hamstring.


Inhibitioin is the name of the game.

To use PRI effectively, you need to be able to change up how you view exercise, at least when you are doing PRI.

You need to look past left hamstring activation. You need to dig deeper and see what is occuring behind the scenes during each exercise.

The Left Sidelying Right Glute MAx is a clamshell. But, at the same time, it’s not a clamshell.

It’s way more than a clamshell.

When you can be comfortable holding those contradictory statements in your mind, and realize they are both true, you’ll find yourself in a PRI mindset and be able to see beyond a right leg going into abduction and external rotation.

You’ll see what else is happening in the frontal and transverse planes that has nothing to do with the leg you are rotating…yet has everything to do with the leg you are rotating.

And you also might be able to understand Ron’s way of speaking if you are fortunate enough to take a seminar he is teaching.