What is the Left AIC Pattern?

The left AIC pattern is the place to start when learning Postural Restoration®.

It is the first and most common pattern to appear when a left hemi-pelvis (also known as left innominate, left ilium, or left pelvis) rotates forward compared to the right and is held there by an overactive chain of muscles that the Postural Restoration Institute® has called the Anterior Interior Chain.

This anteriorly rotated pelvis position orients the entire pelvis, including the sacrum and lower spine, to the right.

As a compensation, our trunk, from T8 (mid-spine and not coincidently, the top of the diaphragm), counter-rotates back to the left so that we can keep our entire body oriented straight ahead.

The picture below is how the pelvis looks in the left AIC pattern.

The left ilium is in a state of left AF/ER (acetabulum on femur external rotation): flexed in the sagittal plane, abducted in the frontal plane, and externally rotated in the transverse plane.

In this position the left hip is in a state of flexion.

The right ilium is doing the opposite of the left. The right ilium is in a state of AF/IR (acetabulum on femur internal rotation): extended in the sagittal plane, adducted in the frontal plane, and internally rotated in the transverse plane.

In this position the right hip is in a state of extension.


Left AIC Pelvis

Pelvic Orientation


Taken together, this left AIC pelvic position orients the entire lumbar-pelvic region to the right

So the left and right sides of the pelvis, sacrum, and lower spine are all oriented to the right.

Visually, the left ilium (left hemi-pelvis) looks flared out and seems to be opening up to the outside world, while the right ilium (right hemi-pelvis) faces inward and is more closed down.

The rest of the body follows this pattern: the entire left side of the body (pelvis, ribs, cranium) is “externally rotated” or “opened up”, or abducted, moving away from the midline of the body.

The entire right side of the body is “internally rotated” or “closed down”, adducted, or being pulled in towards the midline.

Understanding this pattern of external and internal rotation makes PRI much easier to understand.

Leftward Counter-Rotation

The entire pattern is labeled in the picture below with which direction the pelvis, ribs, and neck are going.

But notice that even though there is a leftward counter-rotation of the ribcage and neck, this leftward counter-rotation is occurring on a body that is still oriented right. 

In other words, any leftward rotation that is going on at the ribcage and neck is occurring in the right hemisphere. It doesn’t not mean that the person’s body is in the left hemisphere.

If our body can be lateralized to the right or lateralized to the left, the body is still lateralized to the right.

The counter-rotation of the torso to the left attempts to get our body to lateralize to the left, but it doesn’t happen because the left AIC pattern won’t permit overall lateralization to the left. The pelvis and lower spine is stuck to the right.

You can’t be lateralized left until your center of mass is in the left hemisphere. A left AIC patterned pelvis prevents this from happening.

The Muscles of the Left AIC


The Left AIC pattern is named after the chain of muscles that are over-active.

The Anterior-Interior Chain of muscles are:

  1. Left Diaphragm
  2. Illiacus
  3. Psoas
  4. Rectus Femoris
  5. TFL
  6. Biceps Femoris

The first five muscles on the list are found on the front of the left leg. These five muscles are generally tight and overactive and keep the left hemi-pelvis anteriorly rotated. In training terms the hip is flexed, so there is an anterior pelvic tilt going on.

It is this chain of muscles that we want to turn off.


Learning About the Left AIC pattern


The Left AIC pattern is what is covered in great detail in the Myokinematic Restoration Course, one of PRI’s introductory level courses. During the course, you learn a lot about walking and breathing, and after all, human movement really is walking and breathing.

So the gait and respiration cycle is a big deal.


Gait has two main phases, stance and swing. These two phases are further broken down into phases of stance and phases of swing. All of our movements on two legs consist of either a stance phase leg position or a swing phase leg position. So it’s important to become familiar with these terms.

The Left AIC muscles are active in the swing phase of gait. Just think “hip flexors”.

They are the chain of muscles that have to activate to enable us to swing our left leg forward as we walk. So it’s not as if the Left AIC pattern is bad. We need the Left AIC pattern to kick in when our weight is on our right foot so that we can step forward with our left foot.

The problem with the left AIC pattern is this: it needs to turn “off” when our weight is on our left foot. It should only be active for the left swing phase of gait. Then the left AIC muscles should turn off so that the left “stance muscles” (left hamstring, adductors, glute medius, left internal obliques) can turn on which pull the left pelvis back and into extension. That’s how we should walk.

The left pelvis should be flexed during swing phase of gait and it should be extended during the stance phase of gait. But in the left AIC pattern it stays flexed during both phases of gait. That’s a problem.

This point is fundamental to understanding PRI. In a Left AIC Pattern, the left AIC muscles don’t properly turn off even when our weight is on our left foot. This results in a lack of true tri-planar movement through the pelvis.

In gait terms, in the lower body:

  • On the left side, left swing phase of gait is always “on”. So even when your weight is on the left foot, and the AIC muscles should be “off”, they are still “on”.  If you test positive on the Left Adduction Drop Test, we know your left hemi-pelvis is stuck forward, and it is the Left AIC chain of muscles that are holding it forward (primarily the psoas). So the Left AIC muscles are holding you in the Left AIC pattern.
  • On the right side, right “stance” phase of gait is always “on”. The muscles that hold you in stance phase tend to be overactive. Muscles such as your right adductor magnus and the extensor fibers of the right glute max tend to be short and strong. Conversely, the right leg’s AIC muscles are actually inhibited. In case you hadn’t considered it, the right leg has an AIC chain of muscles and an AIC pattern. However, it is inhibited. It actually needs to be turned “on”. However, it is generally turned “on” by turning the Left AIC pattern “off”.

In Summation


The Left AIC Pattern is one in which our left anterior interior chain of muscles is constantly turned on. This holds the left hemi-pelvis in an anteriorly rotated position compared to the right side.

This Left AIC Pattern also corresponds to the left swing phase of gait. The left AIC chain of muscles that activate to swing our leg forward through the air are the same muscles that hold our left pelvis anteriorly in the Left AIC Pattern.

The consequences of this pattern, where the left hemi-pelvis stays forward and never moves back, means that the Right AIC muscles remain inhibited and the right side of the pelvis gets stuck posteriorly. When a left pelvis doesn’t fully move back, and a right pelvis never fully moves forward, we do not have true tri-planar movement, and thus must move through compensation.

No matter what else you do in PRI, you have to re-position the left hemi-pelvis by bringing it posteriorly from it’s anteriorly rotated postion, and then achieve true and full AF/IR.

Without true and full left AF/IR, you will be forced to move with compensation. This is a very important point. One way or another, your body will find the movement it needs. It likely won’t be balanced between the left and right sides of our body. Thus compensation will have to occur.

When our body decides it can no longer compensate adequately for this loss of tri-planar movement, our movement quality decreases and we may start to feel impingement or muscular tension based pain. When things get more extreme, compensations that occur all the way up into the neck and head can lead to neck pain, headaches, vestibular and balance issues among others.


If you need help, I offer on-on-one PRI training sessions and online Skype consultations. Feel free to e-mail me at Nealhallinan@gmail.com for more information