What is actually inside an active trigger point?

Instead of arguing about what a nodule is from the outside, one line of research put a microanalytical needle into it. The technique sampled the fluid around active trigger points in the upper trapezius and compared it with latent points and normal muscle in the same subjects.

Active points showed lower pH and raised concentrations of substances associated with nociception and inflammation, including substance P, CGRP, bradykinin, serotonin, noradrenaline and several cytokines.

The follow-up study sampled a remote, clinically normal muscle as well — the gastrocnemius, in subjects whose active point was in the neck. Several markers were raised there too, which is hard to explain with a purely local lesion and points toward a sensitised nervous system alongside the local problem.

That is the practical reason a stubborn neck trigger point often needs sleep, load and stress addressed as well as hands on the tissue.

These are small-sample studies in a limited number of muscles, and a chemical signature is not the same thing as a diagnostic test. What they support is that palpable, painful points are not simply an examiner's imagination: something measurable differs between active points, latent points and normal muscle.

Read together with the integrated hypothesis, they give a coherent working model — local energy crisis and sensitising chemistry, amplified centrally — without claiming the case is closed.