I had been looking into what causes myofascial trigger points and pain and how working on them relieved the pain. I came across this study, mechanisms of myofascial pain, which gave some great insights into what causes a myofascial trigger point, what keeps them hanging around, what causes them to be painful, and how to get rid of them.
Some of the key things I noted:
Trigger points may occur from muscle overuse, trauma, psychological stress.
They seem to do two main things:
Reduce the excitability of the central nervous system
The sustained contraction leads to increased metabolic stress and reduces blood flow. This increases myokines, inflammatory cytokines and neurotransmitters.
Working on a trigger point:
Disrupts dysfunctional endplates
Increase sarcomere length (too much contraction from sarcomere increases myofascial trigger point)