Local Facilitation
According to Korr a trigger point is a localised area of somatic dysfunction which behaves in a facilitated manner, i.e. it will amplify and be affected by any form of stress imposed on the individual whether this is physical, chemical or emotional.

A trigger point is palpable as an indurated, localised, painful entity with a reference (target) area to which pain or other symptoms are referred.

Muscles housing trigger points can frequently be identified as being unable to achieve their normal resting length using standard muscle evaluation procedures The trigger point itself commonly lies in fibrotic tissue, which has evolved as the result of exposure of the tissues to diverse forms of stress.

Treatment Methods
A wide variety of treatment methods have been advocated in treating trigger points, including inhibitory pressure methods (Nimmo , Lief) acupuncture and/or ultrasound (Kleyhans and Aarons), chilling and stretching of the muscle in which the trigger lies (Travell and Simon), procaine or xylocaine injections (Slocumb), active or passive stretching (Lewit), and even surgical excision (Dittrich).

Clinical experience, confirmed by the diligent research of Travell and Simons, has shown that while all or any of these methods can successfully inhibit trigger point activity short-term, in order to completely eliminate the noxious activity of the structure more is often needed.

Common sense as well as clinical experience dictates that the next stage of correction of such problems should involve reeducation (postural, relaxation etc) or elimination of factors which contributed to the problem's evolution. This might well involve ergonomic evaluation of home and workplace as well as reeducation methods mentioned above.

Travell and Simons have also shown that whatever initial treatment is offered to inhibit the neurological over-activity of the trigger point, the muscle in which it lies has to be made capable of reaching its normal resting length following such treatment or else the trigger point will rapidly reactivate.

In treating trigger points the method of chilling the offending muscle (housing the trigger) while holding it at stretch in order to achieve this end was advocated by Travell and Simons, while Lewit has espoused the Muscle Energy method of a physiologically induced post-isometric relaxation (or reciprocal inhibition) response, prior to passive stretching. Both methods are commonly successful, although a sufficient degree of failure occurs (trigger rapidly reactivates or fails to completely ’switch off’) to require investigation of more successful approaches.

One reason for failure may relate to the possibility of the tissues which are being stretched not being the precise ones housing the trigger point.

A popular method for achieving tonus release in a muscle prior to stretching involves introduction of an isometric contraction to the affected muscle (producing post isometric relaxation) or to its antagonist (producing reciprocal inhibition).

The original use of isometric contractions prior to stretching was in Proprioceptive Neuromuscular Facilitation Techniques (PNF) which emerged from physical medicine in the early part of the 20th Century. In most forms of Muscle Energy Technique (MET) methodology, derived from osteopathic research and clinical experience, a partial (not full strength) isometric contraction is performed prior to the stretch in order to preclude tissue damage or stress to the patient and/or therapist which PNF quite frequently produces.