The Internal Obliques and Central Zone Core Stabilization
By Perry Nickelston, DC, FMS, SFMA
We often neglect the role of the internal obliques in central zone core stabilization. Why? It takes a backseat to the more trendy and popular research on the transvere abdominis; it rarely, if ever hurts, so people don't consider it a problem; and it's not as visible as the external obliques, leading to the "out of sight, out of mind" factor. That's really a shame, because the internal oblique is a linchpin to core stabilization and force control of the lumbar spine, thorax, pubic symphysis and sacroiliac joint.
Rotation / Force Control and Mobility
Probably the most important role of the internal oblique is eccentric deceleration of contralateral rotation of the spine, otherwise known as "anti-rotation." The ability to decelerate and stabilize the spine against forces that twist it is critical to preventing spinal injury.
The human gait cycle is all about controlling rotation. Dysfunctional gait patterning will occur if the internal and external obliques are inefficient, causing improper generation, absorption, dispersion, and release of force. Altered force control is a catalyst for total-body compensation of tightness, stiffness and decreased range of motion in an attempt to gain stability. The lack of proximal stabilization in the core decreases optimal distal mobility needed for movement patterning.
If you don't own your obliques, you don't own walking. If you don't own walking, you don't own movement. If you don't own movement, you don't own your spine. It's that simple.
Let's take a closer look at some of the important actions and role the internal obliques play in movement. Rotation control is what this muscle lives for. Eccentric control is the movement linchpin. It maintains eccentric movement deceleration of extension of the spine; eccentric deceleration of contralateral flexion of the spine; and eccentric deceleration of pelvic anterior tilt, lumbosacral extension and sacroiliac counternutation. This deceleration function is pivotal in preventing hyperextension and spinal facet joint compression.
What about concentric movement? The internal obliques work with the contralateral external oblique to rotate the spine. Without this co-contraction teamwork, the internal oblique will produce more lateral flexion, altering the vulnerable frontal plane of stability.
Because the internal and external obliques are the primary rotators of the spine, they are the keystones of thoracic spine mobility. The internal obliques are synergists to trunk flexion, working with the external obliques and the prime mover rectus abdominis. They are synergists for lateral flexion of the spine with the same-side external oblique, quadratus lumborum and lumbar paraspinals. A quadratus lumborum muscle spasm may be a result of inhibition in the oblique muscles.
The internal obliques are an integral part of the intrinsic reflexive core stabilization system of the body, which is responsible for maintaining intra-abdominal pressure (IAP). They attach via fascial slips to the diaphragm, transverse abdominis and thoracolumbar fascia, contributing to central zone core stabilization.
If the internal obliques are inhibited, you often see a compensatory facilitation of the thoracolumbar fascia, which may cause an alteration in proper sequencing of the posterior oblique subsystem (gluteus maximus, latissimus dorsi, thoracolumbar fascia). When this system is dysfunctional, people often complain of injuries to the hips and shoulders from lack of force control.
A common, but often-overlooked sign of oblique inhibition is breath holding during simple movement patterns in an attempt to gain stability via a defective intra-abdominal pressure system. When assessing patients with simple movements such as gait, single-leg stance, flexion and extension, etc., notice if they are holding their breath. If so, it is an indication of dysfunction in the intrinsic stabilization subsystem. Adding core stability correctives to your care program is indicated.
Evaluating the Internal Obliques
How can you evaluate the internal obliques? A good baseline is observation of movement and assessing muscle strength. Several options include:
Help Build a Foundation of Core Stabilization
Including internal oblique assessments and correctives into your program can make powerful changes to your clinical outcomes. If you find inhibition in the obliques, add regressed activation and strengthening exercises to your care program at the appropriate time. Pain-free, precise movement patterns are the goal.
It's not about how many repetitions can be done wrong. Two to three quality repetitions are better than 10-15 done poorly. Once your patient can perform a pain-free, symmetrical corrective pattern of movement, you should see a more optimal foundation of core stabilization.
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