What is the Left AIC Pattern?

In order to walk, humans must “ground and rotate”.

We put our weight on the right foot and then rotate our upper body to the left as we step forward with the left foot.

Then we put our weight on the left foot and rotate our upper body to the right as we step forward with the right foot.

This results is one foot being placed in front of the other in a continuous cycle of perfectly coordinated “ground and rotate” muscle activity that moves us forward.

It seems pretty simple.

Until the patterns show up.

The Left AIC pattern 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 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, called the right BC pattern, 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 with my body’s center of mass still to the right.

The counter-rotation of the torso to the left attempts to get our entire body to the left, but it doesn’t happen because the left AIC pattern won’t permit overall movement to the left.

The pelvis and lower spine are stuck to the right.

You can’t be truly on your left leg until your pelvis, spine, and neck can be free to rotate to the left.

A left AIC patterned pelvis prevents this from happening.

And this is what I see all the time. People who are simply stuck in a state of a right legged “ground and rotate” muscle activity.

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.

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.

When a pelvis doesn’t fully move back on the left, and a pelvis never fully moves forward on the right, we do not have true tri-planar movement (movement in three planes of motion), and thus must move through compensation. It’s the compensatory movement that eventually breaks our body down and causes pain.

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 joint and muscle pain, or just varying amounts of tension, in various areas of our body.

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.

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”.

The picture above 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.

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.