Anterior Oblique Subsystem Integration

By Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

The Anterior Oblique Subsystem (AOS) is comprised of:

  • External Obliques
  • Abdominal Fascia/Linea Alba
  • Contralateral Anterior Adductors
  • Internal Obliques
  • Rectus Abdominis
  • Note: The internal obliques and rectus abdominis are not traditionally viewed as muscles of the AOS.  However, based on my considerations of anatomy, function, and available research, and observations in practice, adding these muscles to this subsystem adds congruence to our understanding of muscular synergies, motor behavior, and predictive models of movement impairment.

Function (Brief):

Stabilization of the anterior kinetic chain (including the joints of the pubic symphysis, hip and lumbar spine), transfer of force between lower and upper extremities, integrated (whole body) pushing movements, “turning-in” of the kinetic chain, eccentric deceleration of total-body supination.

Functional Arthrokinematics:
The Anterior Oblique Subsystem (AOS) is an important stabilizer of the anterior kinetic chain.  This subsystem has little direct effect on joint arthrokinematics (when compared to the Posterior Oblique Subsystem (POS) and the sacroiliac joint); however, it is indirectly involved in stabilization of the lumbar spine, thoracic spine, rib cage, pubic symphysis, and hip joint.

The AOS is responsible for eccentric deceleration of rotation and extension of the lumbar and thoracic spine – a 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, pushing motions.  As an anterior pelvic tilt includes lumbar spine extension, sacroiliac joint (SIJ) motion, and if not symmetrical may include rotation; any dyskinesis of the SIJ, lumbar spine, or change in pelvic rotation may indicate AOS involvement.

The AOS directly stabilizes the pubic symphysis, although the most notable relationship in the AOS synergy relative to this joint is the fascial continuity between rectus abdominis (a muscle not traditionally viewed as an AOS muscle) and the adductor longus.  Although relatively rare, pubic symphysis dyskinesis does occur and can be painful.  Optimal function of the AOS bilaterally, ensures control of rotation, superior/inferior glide, and other accessory motions at the pubic symphysis associated with the normal pelvic torsion during gait.

Asymmetrical dysfunction in the AOS may lead to dyskinesis of 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, anterior or posterior tilting of one or both sides of the pelvis, and dyskenisis of the pubic symphysis.  Note that asymmetrical postural dysfunctions like these have been correlated with injury.  At the very least, these dysfunctions will increase strain on the human movement system leading to pattern overload and the cumulative injury cycle.

Integrated Function:

These muscles play an important role in transferring force between lower and upper extremities and stabilizing the