Getting down to the CORE!!
What is your Core?
It is defined as the center or “core” of your body. It is the “powerhouse” around which all limb movement is performed. It consists of 29 pairs of muscles as well as boney, ligamentous, and discs structures that support the lumbo-pelvic-hip complex in order to stabilize the spine, pelvis, and kinetic chain during functional movements. In short, it’s pretty important!
What is the function of the Core?
The core functions to provide both stability and mobility. It can generate forces in order to complete a sit-up as well as provide spinal stability as you reach your arms overhead. The muscles that are most important in providing core stability can be divided into two groups: the primary stabilizers and the secondary stabilizers. The primary stabilizers are the transversus abdominis in the deep abdominal region and the multifidus muscles which are deep in your back and attach directly to each vertebrae in the spine. The secondary stabilizers are the obliques in the front, the quadratus lumborum & lumbar paraspinals in the back, the pelvic floor muscles at the bottom, and the diaphragm at the top.
So what does the research say about the Core muscles?
Current research has promoted the transversus abdominis (TrA) and the multifidus as the primary stabilizers of the spine.(1,4,6,8,9) The TrA is the deepest of the abdominal muscles and, when contracted, it increases tension of the thoraco-lumbar fascia, it increases intra-abdominal pressure, and increases spinal stiffness in order to resist the forces that act upon the spine(4,7) The multifidi span from 1 to 3 vertebral levels and attach one vertebrae directly to another. As a result, they provide the largest contribution to inter-segmental stability.(4,9) The TrA and multifidus have been found to activate prior to limb movement in order to prepare and stabilize the spine(1,4,9) and it has been shown that the EMG activity of the TrA may be delayed in patients suffering with chronic low back pain (LBP).(7) The TrA is activated regardless of the direction of trunk or limb movement(4) and this is the reason why performing spinal stabilization exercises in multiple planes of motion can be so effective. A significant reduction in the cross-sectional area ie atrophy of the multifidi as well as poor motor control of the TrA has been associated with patients with acute or chronic LBP.(6.9) Patients with LBP who did not receive exercises specific for the multifidi continued to have atrophy of the multifidi even after 6 weeks of being painfree as compared to the increases in multifidi cross-sectional area in those that performed the exercises.(6,9) In other words, just because your pain is gone does not mean that your muscles are functionally recovered. One of our primary objectives in physical therapy is to prevent FUTURE episodes of LBP! So how do we do it?
How do we test the Core?
Unfortunately, there is not a research-proven, valid testing regimen for core stability. However, Shirley Sahrmann has proposed a test called the Sahrmann Core Stability Test which is the most common test of function. It involves the use of a pressure cuff placed under the lumbar spine to measure one’s ability to maintain pelvic neutral while performing five exercises of progressive difficulty. The chart is included below.
How do we perform spinal stabilization exercises?
In physical therapy, we utilize the concept of a neutral spine while performing spinal stabilization exercises. Every joint has what we call a “resting” or “open-packed position”. It is the position of a joint when the joint spacing is maximized and the resistance from boney or ligamentous structures is the least. These are the fundamentals of Orthopedic Manual Therapy. In the following video, we will review the concept of the Functional Neutral Position as well describe how to activate the transverses abdominus and multifidi muscles in mutiple positions.
So what are the BEST evidence-based, core stabilization exercises?
1. Allison GT, Morris SL, Lay B. Feedforward responses of transversus abdominis are directionally specific and act asymmetrically: Implications for core stability theories. JOSPT. 2008; 38: 228-237.
2. Ekstrom RA, Donatelli RA, Carp KC. Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises. JOSPT. 2007; 37: 754-762.
3. Escamilla RF, Babb E, Dewitt R. Electromyographic analysis of traditional and nontraditional abdominal exercises: Implications for rehabilitation and training. Physical Therapy. 2006; 86: 656-671.
4. Faries MD, Greenwood M. Core Training: Stabilizing the Confusion. Strength and Conditioning Journal. 2007; 29: 10-25.
5. Hall L, Tsao H, MacDonald D. Immediate effects of co-contraction training on motor control of the trunk muscles in people with recurrent low back pain. Journal of Electromyography and Kinesiology. 2007; 19:763-773.
6. Hides J, Stanton W, McMahon S. Effect of stabilization training of multifidus muscle cross-sectional area among young elite cricketers with low back pain. JOSPT. 2008; 38: 101-108.
7. Hodges P, Kaigle A, Holm S. Intervertebral stiffness of the spine is increased by evoked contraction of transversus abdominis and the diaphragm: In Vivo porcine studies. SPINE. 2003; 28: 2594-2601.
8. Okubo Y, Kaneoka K, Imai A. Electromyographic analysis of transversus abdominis and lumbar multifidus using wire electrodes during lumbar stabilization exercises. JOSPT. 2010; 40: 743-750.
9. Stanford M. Effectiveness of specific lumbar stabilization exercises: A single case study. Journal of Manual and Manipulation Therapy. 2002; 10: 40-46.