Lumbopelvic stability influenced by Serratus Anterior
Western medicine often unintentionally depicts the body as separate systems functioning within one body. The way anatomy and physiology is taught supports this, as well as, the current medical model with specialist for each region or system. In regional anatomy, I was taught individual muscles with a specific origin, action, insertion, and innervation. This is fine for learning the basics, but does not come close to depicting a human’s movement system. In reality the muscles have beautiful continuity along fascial planes or lines. These planes/lines are depicted in a number of texts, one being Anatomy Trains. In his book, Thomas Meyers outlines various fascial lines and describes the body as a tensegrity structure with the muscles, connective tissue, and fascia pulling in and the skeleton pushing back out. With visualization of these structures it becomes apparent the potential effects one region or muscle can have on another region of the body.
The Postural Restoration Institute offers another perspective of polyarticular muscle chains. Put simply, they view most polyarticular muscle chain activity to be driven by respiratory function and sensory input. By altering respiratory patterns and sensory input, one can manipulate muscle chain recruitment and movement patterns. An example of this can be use of a forced exhalation with serratus engagement to help reverse externally rotated, flared ribs and excessive lordosis (and anterior pelvic tilt).
For individuals that demonstrate an excessive lumbar lordosis or potentially hinge at L5/S1 and L4/5 during hip/knee flexion loading tasks, activating the serratus anterior in conjunction with the obliques can help produce a neutral, rigid trunk. Engaging the serratus anterior with a stabilized scapulae will retract the ribs while simultaneously creating fascial tightness with the interdigitating external oblique and deeper internal oblique. The internal obliques will also pull an elevated rib cage towards the anterior rim of the pelvis.
Achieving stability with a neutral lumbopelvic complex will have significant implications. It will decrease stress on the lumbar facet joints and pars interarticularis and simultaneously increase the size of the intervertebral foramen reducing neural compression. Reducing rib flare can promote proper vertical alignment of the respiratory diaphragm over the pelvic diaphragm (pelvic floor) for proper synchronization of core muscles (which includes the pelvic floor!) with respiration. Proper pelvic position equates to proper acetabular position on the femoral head and can decrease intra-articular impingement and stress on the labrum.
Understand by achieving this, an individual’s strategy for achieving stability and producing force will be compromised. This will challenge an individual to create a rigid trunk via muscle chains rather than osseous approximation. The length tension relationships of the glutes and hamstrings will differ from the previously anteriorly tilted pelvis. Because of the muscular demand to stabilize the trunk and altered length tension relationships of lower extremity muscles, an individual’s ability to generate force often decreases initially. This can be practiced with use of a band resisting protraction and exhalation to engage the serratus anterior and obliques during a simple body weight squat or hip hinge.
In the article I list below (out of my alamatur Sagnasty and by some of my former professors) serratus anterior engagement is shown to increase with simultaneous trunk and lower extremity activation. Given the fascial lines do not function unidirectionally, this demonstrated concept could be reversed to increase trunk stability and proper lower extremity (glute/hamstring) muscle recruitment by engaging a serratus anterior muscle.
It is great to be evidence based, but I like to be evidence lead. Try applying some of these ideas to your own training/rehab.
