The Left AIC Pattern

As a personal trainer, I spend my life assessing posture; whether that be during a one to one session with a client or when something stands out to me in a random person. The trainer in me asks “what does that posture presentation mean?” or “What is causing that issue?”. I think as trainers we are all guilty of this occasionally. Following my hip surgery (see my article titled Never Ignore Chronic Pain) and during my time off work I began to look deeper into hip anatomy and its relationship with breathing mechanics. I then stumbled upon the term Left Anterior Interior Chain or Left AIC. In laymans terms this refers to a left to right asymmetry involving the Trunk, ribs, spine, pelvis and hip joints. Have you ever noticed how some people tend to stand on the right leg and shift their centre of mass over to that side? The image below illustrates this further:

Image from Boyle, K.L. (2013) CLINICAL APPLICATION OF THE RIGHT SIDELYING RESPIRATORY LEFT ADDUCTOR PULL BACK EXERCISE, International Journal of Sports Physical Therapy,  8(3): 349–358

I’m sure now you recall seeing this posture in others or indeed realise that you yourself adopt the same posture when standing still. This is a classic sign of a left AIC pattern. The reference to side (left) represents the the polyarticular chain of muscles on the left that are in a suboptimal position compared to the same muslces of the right. (Polyarticular meaning an unbroken chain of muscles crossing more than one joint). Anterior is used because this chain of muscles ( hemi‐diaphragm, iliopsoas, tensor fascia latae, vastus lateralis, and bicep femoris) are anterior or in front of the spine and Interior is used to describe their posterior and deep positioning relative to the rib cage.

The pelvis and the sacrum will be both be oriented to the right. See the video below from fellow Postural Restoration Insitute enthusiast Neil Hallinan for an explanation:

Now what of the right side you may ask! Well firstly there is such a thing as a Right AIC pattern, which would be represented by a left side dominance. However this is not as common, mainly due to to the fact that our diaphragm is stronger on the right- therefore the trunk is more inclined to rotate to the right, as seen in the above image.

The Left AIC presentation usually co-exists with something known as Right Brachial chain- which consists of the neck muscles, pecs and deltoids, the anterior- lateral intercostals and the right side of the diaphragm. Note the elevation of the left shoulder in the above image and the contracture of the right side neck muscles- almost acting as counterbalance because of the right leg dominance. Someone with this posture presentation would usually present rib flare on the left- and suboptimal breathing mechanics and and inability to maintain a neutral pelvic and ribcage posture when performing exercises such as deadbugs and planks. So establishing a Zone of Apposition (ZOA) would be the first port of call (See my first article titled Approaches to Core Stability part I). The Postural Restoration Institute (PRI) provide more information on the Left AIC Right Brachial Chain presentation as well as third part to the presentation- Posterior Exterior Chain (PEC), but that is beyond the scope of this article. Check out their website: https://www.posturalrestoration.com/ for more details on the concepts and courses!

Observations

Apart from visual observations that may look something like the image above, other things to look out for are:

  • Positioning of the left knee ahead of the right when sitting, laying down
  • Right leg dominance when standing up from a seated position
  • Slapping of the left foot to the groud during gait (someone that walks as though they are kicking a football with their left foot). This suggests an inability of the pelvis to change it’s position on the left and right side as a person walks.

One way to check for a potentional Left AIC posture is to see how far you can pull your left femur (thigh bone) into the hip socket compared to the right:

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