Muscle Of The Month – Posterior Oblique Subsystem

As discussed in our blogs on the Lateral Subsystem and the Deep Longitudinal Subsystem, muscles rarely work in isolation. Instead, the nervous system recruits them in groups or synergies.

Today’s blog is on the Posterior Oblique Subsystem, one of the four common muscle synergies. It resembles a cross, with two bands extending from each shoulder to the opposite hip, encompassing the gluteus maximus and latissimus dorsi, which both connect to the thoracolumbar fascia.

The origination and insertion of the Posterior Oblique Subsystem

• Gluteus maximus – origin: posterior of the sacrum, ilium and coccyx; insertions: gluteal tuberosity of the femur and iliotibial tract.
• Latissimus dorsi – origin: spinous processes of T7-T12, iliac crest, thoracolumbar fascia, inferior angle of the scapula and inferior three or four ribs; insertion: floor of the intertubercular humerus.
• Thoracolumbar fascia – origination: the spinous processes of the thoracic and the lumbar vertebrae; insertion: median crest of the sacrum and muscle fascias such as the quadratus lumborum, erector spinae and latissimus dorsi.

The action and basic functional movement of the Posterior Oblique Subsystem

Working in conjunction with the Deep Longitudinal Subsystem, the Posterior Oblique Subsystem distributes transverse plane forces when the core and back are rotated. This is particularly useful for throwing or hitting a ball and for twisting movements, such as those found in sports like golf, tennis, baseball, and boxing.

This system is also employed when we walk or run, transferring forces from the transverse plane into propulsion in the sagittal plane, and it provides stability for the lower spine and sacroiliac joint (SIJ).

Problems associated with the Posterior Oblique Subsystem

If the Posterior Oblique Subsystem doesn’t correctly support the spine and sacroiliac joint (SIJ), it can lead to tight muscles and pain in the lower back, inflammation and pain in the SIJ, or muscle spasms causing pain in the buttocks.

Other issues associated with a weak or injured posterior oblique subsystem can include hamstring strain, which is often caused by increased tension in this muscle.

If a personal trainer or fitness instructor notices that a client has rounded shoulders, internally rotated hips, or long reaction times when accelerating and decelerating, it may suggest work is needed on their posterior oblique subsystem.

Exercises to strengthen the Posterior Oblique Subsystem

The best exercises for the posterior oblique subsystem are rotational activities performed in the transverse plane, with particular focus on the gluteus maximus and contralateral latissimus dorsi.

Examples include:

• One arm, single leg cobra
• Bird dog exercise
• Single-leg deadlift with dumbbell or cable
• Split squat or rear foot elevated split squat with dumbbell or cable
• Squat to row (advance to unstable squat with unilateral row)
• Reverse lunge with opposite arm overhead press
• Curtsy lunge
• Step up with cable
• Medicine ball reverse lunge and shot put