To evaluate the feasibility of three new, objective measurements for characterizing trigger points (TrPs).

Although TrPs affect millions of individuals, we do not understand the mechanisms underlying the course of this condition. Furthermore, most pain studies rely on subjective patient scores as the primary outcome. To address these gaps, we aim to employ three entirely objective and quantitative assessment methodologies to assess these entities.

Here we present results from our first group of healthy subjects whose data have been analyzed for repeatability. This novel data set will assist us in moving toward full implementation of a standardized TrP assessment protocol.

We performed testing of the three modalities on the right trapezius muscle in healthy participants during two separate visits. Electrical impedance myography (EIM) noninvasively evaluates muscle properties using a painless electrical current. Quantitative muscle ultrasound images translate the brightness of muscle scans into a numerical value, the grayscale level. Myofiber excitability testing (MET) quantifies changes in muscle fiber conduction properties in response to various electrical conditioning stimuli. Intra-class coefficients (ICCs), Bland-Altman analysis and mean percent difference were calculated as a reflection of reliability for each of these modalities.

Sixteen healthy participants (10 men, 6 women) with mean age±SD 52.6±16.7 years were enrolled. There was a strong intraclass correlation for the EIM phase angle values between first and second visit, ICC = 0.96, and a mean percent difference of 9.35±8.89%. Reproducibility of grayscale also demonstrated positive correlation between the visits, ICC = 0.92, with mean percent difference 4.47±3.78%, as did MET with mean percent difference 3.47±0.37%.

The initial findings indicate the promising use of EIM, grayscale, and MET as potential diagnostic biomarkers for TrPs.