Extension Bias

Back arching position
Back arching position. Mike Harrington/Collection:Stone/Getty Images

Extension Bias

Have you ever noticed how some positions make your back feel better, while others make it feel worse?  For certain common back problems such as herniated disc, facet arthritis, sacroiliac joint pain, and others, known associations with specific positions exist.  Physical therapists, as well as personal trainers in the know, use this information to help their clients and/or patients manage symptoms at home, at work, and while exercising.

Directional Preferences

These directional preferences, as they are called in the spine rehab world, are part of a movement based approach to categorizing low back pain that allows your therapist to watch how you stand, sit, walk and move, and to listen to what you have to say about your pain.  Your therapist uses the information gleaned to come up with a treatment plan that works for you.

The approach is called the "non-pathoanatomical system" of classification.  There's also a pathoanatomical approach that is more about looking at MRIs, CT scans and the like to determine how best to treat your symptoms.  

The McKenzie system, widely in use by physiotherapists around the world, is perhaps the best example of a non-pathoanatomical classification system. Book Review:  Treat Your Own Neck, by Robin McKenzie

So which works better - the pathoanatomical approach, i.e. the definitive read on what's going on in your structures, or the non-pathoanatomical approach, which is obviously more patient-centric?

The pathoanatomical approach dominates the clinical landscape, but a number of professionals in the field assert that the system has flaws.  In their clinical practice guidelines for low back pain, for example, the American Physical Therapy Association says the non-pathoanatomical approach to classifying back pain is made more difficult by the number of false positives that are found on diagnostic imaging tests.


To illustrate their point, the authors of the guidelines report that in 20% - 76% of people with no sciatica who underwent imaging tests herniated discs could be found. And, in 32% of patients who had no symptoms at all, either disc degeneration, bulging or herniation, or facet joint hypertrophy or spinal nerve root compression was detected.  The authors add that it's possible for people to get low back pain while their x-rays or CT scans remain unchanged.  They conclude by saying that even when an abnormality is found on a film, linking it to the patient's condition and/or determining its cause, is elusive - and not very useful in helping that patient feel better or return to functioning.

Does Your Back Favor Extension?  (And What To Do About It)

Along with extension bias, there are two other types: Flexion bias and non-weight bearing bias.  If your symptoms decrease or go away altogether when you arch your back, your back condition likely has an extension bias.  

In general, disc problems and posterior longitudinal ligament injuries have extension biases.

 Ways you might employ this information if you have either of these two injury types include:

  • Lying in the prone position, which arches (extends) the back. 
  • Minimize or eliminate activities in which the spine has to flex, such as rounding your back when you pick things (or people) up from the floor or a chair.
  • Ask your doctor or physical therapist about extension bias and how you might position your spine to manage your back pain and other symptoms.

Related: Workout Routine Hacks for People with Back Pain


Delitto, A., PT, PhD., et. al. Low Back Pain. Clinical Practice Guidelines Linked to the International Classification of Functioning, Disability, and Health from the Orthopaedic Section of the American Physical Therapy Association. J Orthop Sports Phys Ther. 2012.

Dunsford, A., Kumar, S., Clarke, S. Integrating evidence into practice: use of McKenzie-based treatment for mechanical low back pain. J Multidiscip Healthc. 2011.

Kinser, C., Colby, L.A., Therapeutic Exercise: Foundations and Techniques. 4th Edition. F.A. Davis Company. Philadelphia, PA. 2002.

Nachemson, A. Scientific diagnosis or unproved label for back pain patients. Lumbar Segmental Instability. Szpalski M, Gunzburg R, Pope MH eds. Philadelphia: Lippincott William & Wilkins, 297-301.http://www.aptei.com/articles/pdf/IRSAT_1.pdf

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