Biology of Trigger Points: Sentinels for Mechanical Stress

Sentinels for Mechanical Stress

Page 10 of "The Biology of Trigger Points: What they are, what they do, and when and why they occur".

Biology of Trigger Points: Introduction and Contents | Reference List
Previous Page | Next Page

About the Author...

Why donate?
PayPal Membership Not Required!

Trigger Points: Sentinels for Mechanical Stress
So why do trigger points exist? - Trigger points are ubiquitous in both man and animal. Both their locations in muscles and their patterns of transferred pain/inflammation are remarkably similar between individuals. Such uniformity suggests that both the trigger points and their patterns of referral are strongly encoded at the genetic level; that they are in fact there for a purpose. What can that purpose be?

The most likely explanation runs thus:-

"Trigger points are sentinels for mechanical stress that warn the organism to guard the likely associated parts, and at the same time initiate a cycle of acute inflammation that is followed by healing and strengthening of likely associated parts".

For example, the Gluteus minimus (diagram right) is a "side strut" for the leg. If a trigger point in the Gluteus minimus senses that it is being over-loaded, it is entirely appropriate for it to send a message to all of the "side-strut" muscles and ligaments down the entire length of the leg to warn them to also strengthen up.

Diagram:
Trigger points in the Gluteus minimus have the potential, via referred pain and referred neurogenic inflammation to bring about strengthening of the "side struts" of the whole associated leg.
Diagram, Gluteus minimus trigger points and referred pain zone

Diagram, Gluteus minimus trigger points and referred pain zone

Trigger points become active subsequent to the following mechanical stressors:-

Prolonged and/or heavy exertion.
Mechanical irritation such as the prolonged pressure caused by sitting on a wallet.
Trauma, either from a direct blow or from "pulling" a muscle.

All the above are examples of mechanical stress. In each situation, trigger points initiate an integrated process designed to limit further damage and to bring about healing and strengthening, thus:-

Initiation of the Guarding Response:
Tissues both near and far are "triggered" to send out pain warnings that encourage the organism to take it easy, to not put too much pressure on the damaged part or parts, to perhaps learn a wiser movement pattern.

Initiation of the Cycle of Repair and Strengthening:
Inflammation is triggered (by mechanical and neurogenic means locally see "taut band" and by neurogenic means in referral zones, see "neurogenic inflammation"), and initiates the cycle of tissue destruction followed by repair and strengthening that is the hallmark of the self repairing biological machine. It is not just the locus of the trigger point that attempts to inflame, then heal and strengthen: The referral phenomenon means that muscles and tendons as far removed as the opposite ends of the affected limb are "triggered" into an appropriate cycle of tissue inflammation followed by repair and strengthening.

At least that is how it would be in a perfect world! There is an objection to this hypothesis, which needs to be answered...

Trigger Points: when Initiation of Inflammation and Repair fails to switch off
If Trigger Points have such a beneficial effect in terms of response to trauma, how come so many people are afflicted with chronic trigger point induced pain and disability? - The answer lies in that word "chronic": Trigger points should only remain active for a period of perhaps one to three days. After that, the trigger points should "down-regulate"; pain enforced rest should be replaced by resumed activity, and trigger point triggered acute inflammation should progress to the chronic repair and strengthening phase. The following two sections explain why this may down-regulation may not readily occur.

Biology of Trigger Points: Sentinels for Mechanical Stress
© Bruce Thomson
Return to Top