Influence of Low-Intensity Galvanic Current in the Upper Trapezius on Pressure Pain Threshold and Surface Electromyography

To compare the effects of low-intensity galvanic current on pressure pain threshold levels and electromyographic pattern (basal and peak) in individuals with myofascial trigger points in the upper trapezius muscle.

This multiple-case study involved 16 participants with active MTrPs in the upper trapezius muscle. The participants were assessed using algometry with the Pressure Pain Threshold (PPT) outcome measure and surface electromyography for baseline peak electrical activity (EMG-BEA-Peak) and root mean square (EMG-BEA-RMS), as well as during isometric electrical activity with peak signal (EMG-IEA-Peak) and root mean square (EMG-IEA-RMS). MTrPs were confirmed via physical examination and algometric measurement pre-intervention. Measurements were taken pre-intervention, 1 minute, and 10 minutes post-intervention. Participants were randomly allocated into two groups: low-intensity galvanic current (n=8) or sham (n=8). The active group was treated with 0.30 mm x 25 mm acupuncture needles. A Shapiro-Wilk test was conducted, followed by independent samples t-tests. Additional analysis was performed using the bootstrapping technique (n=1000, 95% CI, bias-corrected and accelerated [BCa]). The effect size was calculated using Cohen's d, with interpretation: small ( 0.2), moderate (~ 0.5), and large (> 0.8).

No statistically significant differences were found between the groups for the studied variables. However, medium effect sizes (Cohen's d) were identified for EMG-BEA-RMS - Post 1 min and EMG-IEA-RMS - Post 1 min, while a large effect was noted for EMG-BEA-Peak - Post 1 min.

Low-intensity galvanic current showed clinical effects on muscle electrical activity, both basal and peak in isometric contraction, with observable changes immediately post-application. However, these effects were not statistically significant. The short follow-up window may have been a limiting factor, suggesting that studies with longer follow-up periods are necessary.

Low-intensity galvanic current can alter muscle electrical responses, particularly in clinical settings. Despite the limitations, the technique shows potential as an adjunctive treatment, highlighting the need for combination approaches to enhance therapeutic outcomes.