Medical Sciences Stack Exchange is a question and answer site for professionals in medical and allied health fields, students of those professions, related academics, and others with a sound understanding of medicine and healthcare-related sciences. It only takes a minute to sign up.
Sign up to join this community
In Travell and Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual, an energy crisis within a muscle is said to entail the release of sensitizing substances that could interact with local sensory and autonomic nerves. The following sketch from the publication depicts the situation as constituent of a larger, vicious cycle:
Which substances are those? Why does the body release them as a result of an energy crisis?
A chain of events that leads to release of sensitizing substances, according to Dry needling — peripheral and central considerations (PubMed Central, 2011):
...muscle pain would cause spasm of the same muscle, and in turn would cause more pain leading to more spasms.
Sustained contractures of taut bands cause local ischemia and hypoxia in the core of trigger points. (This would result from contracted muscles that compress the blood vessels and thus oxygen supply to the muscles - according to your diagram.)
Low oxygen levels lead to a significant drop in pH.
A low pH...triggers the release of several nociceptive [sensitizing] substances, such as calcitonin gene-related peptide (CGRP), adenosine triphosphate (ATP), bradykinin (BK), serotonin (5-HT), prostaglandins (PGs), potassium, and protons.
Another source mentions histamine as another senzitizing substance.
NOTE: All of the above is merely a hypothesis, so any conclusions drawn from this could be misleading.
