What is the REPEX?


What is the REPEX?

The McKenzie system of diagnosis and treatment for painful mechanical spinal disorders involves the use of repetitive endrange movements which influence the location and intensity of pain arising from the spinal column.

The model developed by McKenzie is based on the concept that intervertebral disc fluid, nucleus or dislocated tissue displaces according to the directional forces applied.  Should displacement occur to such a degree that pain is produced; repeated movements to endrange applied in the opposite direction will reduce such displacement (the Derangement Syndrome).

Where back pain is caused by scarring, contracture or nerve root adherence and fibrosis, (the Dysfunction Syndrome) re-modeling of tissue is possible using repetitive movement.  Treatment by progressive repeated endrange movement is the basis for what have become known as “McKenzie Exercises”.

Limitations, however, have been reported using the McKenzie methods.  Patient fatigue for example, has been cited as a limiting factor.  Because of fatigue, in one treatment session patients are forced to discontinue exercises at the very time when continuation of them would provide progressive improvement or total relief of systems.

A further limiting factor exists where significant loss of movement restricts the patient’s ability to exercise appropriately.  Elderly patients and those with problems in joints of the upper extremity are unable to repeat therapeutic exercises to the maximum potential.  Thus, recovery is retarded or prevented.

The REPEX machine was initiated by McKenzie in 1988 to enhance the effectiveness of repeated endrange movement therapy for mechanical disorders of the low back.  The concept of using continuous endrange passive movement was introduced to enable the lumbar spinal segments to be moved to the full available endrange of passive physiological movement a greater number of times then is physically possible using patient generated exercises.

REPEX can provide up to approximately 10 cycles per minute of flexion or extension or both.

 By applying progressive repeated endrange exercises, patients can frequently experience a rapid centralization, reduction or abolition of pain.  Centralization of pain occurring at the initial evaluation is a reliable predictor of successful outcome. This phenomenon is unique to the McKenzie treatment.  With the use of the REPEX, it is possible to achieve centralization in cases where patient generated exercised carried out over several days have failed to produce change.

A further advantage obtained from the use of REPEX is the ability to rapidly reduce derangement even when movement is significantly obstructed such as occurs in lumbar Derangement Two (Acute Kyohosis).  Prior to the advent of REPEX, curve reversal from kyphosis to lordosis in this acute disorder was achieved slowly over a period of time using careful positioning and mid-range movement as behavior of pain allowed.  With the correct use of REPEX, it is now possible to restore full movement within 20 to 30 minutes.

In the treatment of patients with the dysfunction syndrome, the fine control of REPEX and the unlimited number of delivery cycles provides a remodeling process unobtainable by patient self-generated exercises.

The McKenzie Institute International has been, and continues to trial REPEX in its New Zealand clinics.


Craig Zettergren, PT, MS, MBA is a fellowship trained physical therapist in Mechanical Diagnosis and Therapy for the spine and extremities with the McKenzie Institute.  He has two offices servicing Central Connecticut, the towns ofBristol,Southington, Plantsville Cheshire andMeriden.  TheBristoloffice is located at72 Pine Street, (860) 585- 5800 and theSouthingtonoffice is located at 1090 Meriden-Waterbury Tpke., (203) 272-8490

Personal, Professional, Physical Therapy



1.  McKenzie, R.A.: The Lumbar Spine, Mechanical Diagnosis and Therapy, First Edition, Spinal Publications,                LowerHutt,New Zealand, 1981

  1. Donelson, R.: Murphy, K.,: Silva G.: Centralization Phenomenon: Its usefulness in evaluation and treating referred pain. Spine 15:3, 1990.
  2. Evans, P.:  The Healing Process at Cellular Level.  Physiotherapy 66:8, 1980
  3. McIlwaine, W.A.:  A Technique for Improving Results of Soft Tissue Repair in Low Back Patients Utilizing the LPM 100.
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