PT Tip of the Month
Introduction: Getting to the core of what "core" is
You've probably heard of the term "core" from those infomercials on T.V. that promise to work your core through various mat exercises, yoga, Pilates, or belly fat-busting new moves. Usually these infomercials point to a compilation of muscles around your mid-section and mid- to low-back, but what do these muscles do, and why is so important to have a strong core?
First, we should clarify and define some terms. There are two terms that are used a lot when discussing core: core stability and core strength. Faries and Greenwood (2007) define core stability as the "ability to stabilize the spine as a result of muscle activity," whereas core strength refers to the ability of the musculature to then produce force through contractile forces and intra-abdominal pressure." Thus, it is necessary to have core strength in order to achieve and maintain core stability. Although in the rehabilitation sector, the focus is initially on regaining core stability, and in the athletic and elite sports arena, the focus is on developing core strength, research has indicated that it is important to have sufficient amounts of both stability and strength in order for the body to perform optimally in everyday and sporting activities. The literature describes that inadequate core strength resulting in poor core stability may lead to decreased biomechanical efficiency, increasing the risk for injury. On the other hand, good core strength contributing to sufficient core stability has been suggested to maintain the correct lumbar and pelvic alignment during movement and sport, allowing for more effective mobility of distal segments (i.e. arms and legs).
The core consists of many different muscles that stabilize the spine and pelvis, and according to some authors, include muscles as far up as the scapula and shoulder and as far down as the hips and thighs. These muscles provide a strong foundation for movement of the arms and legs, as well as assist in upright standing, and help to distribute the stresses of weight-bearing. The muscles that share attachments with the thoracolumbar and abdominal fascia form a "hoop" which helps to provide support to the spinal column.
Among different experts, the list of muscles that make up the core varies, however the following are the most commonly identified core muscles in the available literature:
- Rectus abdominis: This muscle is located in the front of the abdomen and often referred to as the "six-pack" muscle in fit individuals. This muscle functions to flex the trunk.
- External obliques: These muscles are located on each side of the abdomen.
- Internal obliques: These muscles are located underneath the external obliques on each side of the abdomen, with fibers that run in the opposite direction of the external obliques.
- Transverse abdominis: These are the deepest abdominal muscles (located underneath the obliques) which have connections to the spine to protect and stabilize the spine from the back and compress from the front.
- Quadratus lumborum: This muscle is located on each side of the spine and assists with lateral flexion of the trunk.
- Erector spinae: Made up of three muscles (iliocostalis, longissimus, and spinalis), this group of muscles runs along the length of the neck to the low back and help to extend the spine.
- Multifidus: These muscles run the length of the vertebral column underneath the erector spinae muscles and help to extend the spine.
- Latissimus dorsi: Largely known as the "swimmer's muscle," this muscle spans the majority of the mid- and low-back on both sides of the spinal column.
- Hip flexors: Made up of a variety of muscles (the major two are psoas major and iliacus), these muscles help to flex the hip.
- Gluteus maximus and gluteus medius/minimus: Located at the back and sides of the hips, these muscles are important in extending and abducting the hip, respectively, and indirectly support the spine.
Pathology: What happens when your core is not working properly?
There has been much research devoted to the importance of core stability and core strength in relation to low back pain. A study by Hodges and Richardson (1996) indicates that delayed contraction of the transverse abdominis muscle results in inefficient muscular stabilization of the spine, as was seen in patients with low back pain. This delay was seen in patients during various upper extremity reaching tasks, leading to the idea that the transverse abdominis is important in generating the necessary spinal stiffness prior to initiating arm movement.
McGill (2002), an expert in spine function and injury prevention and rehabilitation, states that strengthening the back has little association with low-back health. Muscle endurance, on the other hand, has been shown to exert a protective mechanism against future back injuries. Motor control re-training of the spinal stabilizers consists of grooving motion and muscle activation patterns to prepare for challenges encountered in everyday functioning and to enhance low-back health. When these muscles aren't functioning properly, spinal segmental "buckling" can occur, leading to tissue irritation and/or injury. McGill suggests that the goal in preventing low-back pain is to obtain enough stability in the spine by doing exercises to promote correct activation of the deep spinal and abdominal muscles. McGill recommends low-back exercises consisting of low load, high repetitions, although the ideal set varies among individuals. Proper motor control of the lumbar multifidi, transverse abdominis, and obliques/quadratus lumborum are necessary to maintain proper back health and minimize risk of re-injury. Training for performance is a different matter, and you should seek consultation with a physical therapist if that is the focus.
Role of Physical Therapy
Your physical therapist will be able to assess if there are motor control or endurance deficits in the muscles that stabilize your spine and if they are contributing to your current low back pain. During your physical therapy visits, your physical therapist will prescribe various exercises to assist in re-training the timing and activation of these muscles in order to return you to your prior level of activity, with minimal or no pain. If you would like to schedule an evaluation, call 617-232-PAIN for our Brookline office, and 617-325-PAIN for our West Roxbury office to see one of our skilled physical therapists.
Allison GT, Morris SL and Lay B. Feed forward responses of transverse abdominus are directionally specific and act asymmetrically: implications for core stability theories. JOSPT. 2008;38(5):228-237.
Allison GT and Morris SL. Transversus abdominus and core stability: has the pendulum swung? Br J Sports Med. 2008;42:930-931.
Faries MD and Greenwood M. Core training: stabilizing the confusion. Strength Cond J. 2007;29(2):10-25.
Hibbs AE, Thompson KG, French D, Wrigley A and Spears I. Optimizing performance by improving core stability and core strength. Sports Med. 2008;38(12):995-1008.
Hodges PW and Richardson CA. Inefficient muscular stabilization of the lumbar spine associated with low back pain: a motor control evaluation of transversus abdominis. Spine. 1996;21(22):2640-2650.
Kibler BW, Press J and Sciascia A. The role of core stability in athletic function. Sports Med. 2006;36(3):189-198.
- McGill, S.M. (2002). Low Back Disorders: Evidence based prevention and rehabilitation. Champaign, Ill.: Human Kinetics.
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