Trigger point definitions and structure
Many of you are familiar with trigger points. For
those of you who are not, here is a quick review of definitions.
"Myofascial Trigger Point (clinical definition
of a central trigger point): A hyperirritable spot in skeletal
muscle that is associated with a hypersensitive palpable nodule
in a taut band. The spot is painful on compression, and can
give rise to characteristic referred pain, referred tenderness,
motor dysfunction, and autonomic phenomena"(1)
emphasis mine. What this means is that when you, the clinician,
suspect a trigger point, you can palpate for it. It will be hard.
When you locate it, the patient will say "ouch."
"Myofascial Trigger Point (etiological definition
of a central trigger point): A cluster of electrically active
loci, each of which is associated with a contraction knot and a
dysfunctional motor endplate in skeletal muscle"(1)
emphasis mine. What is important is that a trigger point is electrically
different from the surrounding tissue. The same is true for acupuncture
points. These facts suggest a possible mechanism for the effectiveness
of Tandem Point therapy, which will discussed later.
"Attachment Trigger Point: A trigger point
at the musculotendinous junction and/or at the osseous attachment
of the muscle that identifies the enthesopathy caused by unrelieved
tension characteristic of the taut band that is produced by a central
"Key Myofascial Trigger Point: A trigger point
responsible for activating one or more satellite trigger points.
Clinically, a key trigger point is identified when inactivation
of that trigger point also inactivates the satellite trigger point."(1)
"Satellite Myofascial Trigger Point: A central
myofascial trigger point that was induced neurogenically or mechanically
by the activity of a key trigger point. . . . A satellite trigger
point may develop:
- in the zone of reference of the key trigger point
- in an overloaded synergist that is substituting for the muscle
harboring the key trigger point (key muscle) or in an antagonist
countering the increased tension of the key muscle [both previously
called a secondary trigger point], or
- in a muscle linked apparently only neurogenically to the key
C. Chan Gunn, M.D., has also found a linkage between trigger points
and contractures in other muscles on the same myotome, and I will
discuss that linkage further later.
"Taut Band: The group of tense muscle fibers extending
from a trigger point to the muscle attachments. The tension of the
fibers is caused by contraction knots that are located in the region
of the trigger point."(1)
"Referred (Trigger-Point) Pain: Pain that arises in a trigger
point, but is felt at a distance, often entirely remote form its
source. The pattern of referred pain is reproducibly related to
its site of origin. The distribution of referred trigger-point pain
rarely coincides entirely with the distribution of a peripheral
nerve or dermatomal segment."
of a trigger point complex of a muscle in longitudinal section.
The schematic identifies three regions that can exhibit abnormal
tenderness (red). It also illustrates contraction knots that
most likely: make a trigger point feel nodular, cause the
taut band, and mark the site of an active locus. A,
the central trigger point (CTrP) which is found
in the endplate zone, contains numerous electrically active
loci, and contains numerous contraction knots. The local
tenderness of the CTrP is identified by a red oval. A taut
band of muscle fibers extends from the trigger point to the
attachment at each end of the involved fibers. The sustained
tension that the taut band exerts on the attachment tissues
can induce a localized enthesopathy that is identified as
an attachment trigger point (ATrP). The local
tenderness of the enthesopathy at the ATrP is identified by
a red circle with a black border. B, this enlarged
view of part of the central trigger point shows the distribution
of five contraction knots.... In patients, the CTrP would
feel nodular as compared to the adjacent muscle tissue, because
it contains numerous "swollen" contraction knots that take
up additional space and are much more firm and tense than
uninvolved muscle fibers."
Simons DG, Travell JG, Simons LS: Travell & Simons' Myofascial
Pain and Dysfunction: The Trigger Point Manual, Vol. 1,
Second Edition, Williams & Wilkins, Baltimore, p. 70. Reproduced
with the permission of Lippincott Williams
This diagram is based on photographs taken under light microscopy
of canine muscle tender spots that meet trigger point criteria.
The diagram shows attachment trigger points at each end of one muscle
and a central trigger point. Looking within the trigger point, you
can see multiple contraction knots with contracted sarcomeres. David
Simons notes that oxygen is missing from a trigger point. Water
and ions may also be missing.
Source: Oschman JL, Oschman NH: Readings
on the Scientific Basis of Bodywork, Energetic, and Movement
Therapies, N.O.R.A., Dover, NH, 1997 (p. 17). Reproduced
with the kind permission of N.O.R.A.
Painful, palpable nodules may appear in tendons,
especially at the periosteal attachments. During Tandem Point therapy,
these nodules feel and act just like trigger points. I use them
interchangeably with trigger points in muscles. [During Rolfing(TM)
sessions, I have observed that the release of fascial restrictions
is facilitated by pressing acupuncture points.]
Recent research reveals that trigger points are electrically
different from the surrounding tissue. Electromyograph studies show
that active trigger points have (a) intermittent and variable high-amplitude
spike potentials, and (b) a consistently present, lower amplitude
noise-like component, called by David Simons spontaneous electrical
activity.(2) While Simons discusses this electrical
activity as being diagnostic or characteristic of a trigger point,
I would like you to consider that this electrical activity may
be the most important feature of the trigger point, the feature
that perpetuates the trigger point.
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