Anterior Oblique subsystem (AOS)

The Anterior Oblique Subsystem (AOS) is comprised of:

External Obliques
Abdominal Fascia/Linea Alba
Contralateral Anterior Adductors
Internal Obliques
Rectus Abdominis

Function (Brief):

Stabilization of the anterior kinetic chain Which including the joints of the pubic symphysis, hip, and lumbar spine. It transfer force between lower and upper extremities.

Functional Arthrokinetic:

The Anterior Oblique Subsystem plays very important for stabilizing anterior kinetic chain. This subsystem has little effect on joint arthrokinematics .

The AOS is responsible for eccentric deceleration of rotation and extension of the lumbar and thoracic spine –  when there is asymmetrical movement pattern that may lead to facet joint and posterior disk compression and has been indicated in lumbar spine injury.

The AOS is also involved in eccentric deceleration of an anterior pelvic tilt, especially during standing and pushing motions. As an anterior pelvic tilt includes lumbar spine extension with little sacroiliac joint (SIJ) motion. If you find any change in pelvic rotation and SIJ dysfunction which may involve AOS involvement.

The AOS directly stabilizes the pubic symphysis. There is a most notable relationship in the AOS synergy relative to pubis symphysis joint is the fascial continuity.

It provides an optimal function to control of rotation with, superior/inferior glide, and other accessory motions at the pubic symphysis which associated with the normal pelvic torsion during gait.

What happen when AOS dysfunction occurs?

There is asymmetrical movement occur in the lumbar and thoracic spine, SI joint and pubic symphysis via rotation of the spine and/or innominate. This dysfunction may present as


rotation, lateral flexion, a hip hike and, anterior or posterior tilting of one or both sides of the pelvis.

Integrated Function:

These muscles play an important role in transferring force between lower and upper extremities and stabilizing the anterior kinetic chain. The AOS is stressed most during pushing motions. This musculature also functions as an eccentric decelerator of total-body. The importance of decelerating total body supination can be seen during the “loading phase” of a throw or swing.

Motor Behavior of AOS :

In Upper Body Dysfunction the AOS is over-active, But in Lumbo Pelvic Hip Complex Dysfunction we see the AOS is often under-active.

It is over-active in the case of an excessive forward lean of the body while doing squat or under-active as is the case of LLD presenting with an anterior pelvic tilt.

In Upper Body Dysfunction UBD the AOS is overactive/dominant which is paired with under-active/inhibited Posterior oblique subsystem. This may be most obviously seen in those individuals who have excessive thoracic kyphosis.

Overhead squat assessment, an individual will present with upper body dysfunction signs (arms fall forward, scapula elevate). In addition to that when you perform the overhead squat with the hands on the waist the AOS dominance signs will not present (flexion of the lumbar/thoracic spine and/or excessive forward lean).

The increase in latissimus dorsi activity in upper-body dysfunction may lead to an alteration in the motor pattern Which is responsible to stabilize the Lumbopelvic hip complex.

Exercise Selection :

If movement assessment leads to believe that the AOS is underactive (Anterior Pelvic Tilt) consider the following changes to your exercise programming.

wood chop , proactive physiotherapy Core stability

Core: planks, crunches, and chop patterns to the core portion of the integrated warm-up.

If movement assessment leads us to believe that the AOS is Overactive, Excessive Forward Lean during overhead squat consider the following changes to your exercise programming.

Core: It may be beneficial to avoid planks, crunches, and wood chop patterns. Hence spend more time on TVA activation and bridges.

Reference :

1. Dr. Mike Clark & Scott Lucette, “NASM Essentials of Corrective Exercise Training”  2011 Lippincott Williams & Wilkins
2. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition”  2012 Mosby, Inc.
3. Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition  Elsevier Limited, 2004


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