Influence of Percutaneous Microelectrolysis in the Upper Trapezius on Pressure Pain Threshold and Surface Electromyography: A Randomized Sham-Controlled Pilot Trial

Background: Myofascial pain syndrome is a non-inflammatory disorder that manifests as referred pain and stiffness, with its primary feature being the presence of myofascial trigger points (MTrP). Several methods exist to treat this syndrome, and one of the earliest described techniques involves the invasive use of direct current. Study design: A randomized, double-blind, sham-controlled pilot trial. Participants: Adults (18–48 years) with active myofascial trigger points (MTrPs) in the upper trapezius were recruited. Exclusion criteria included prior shoulder or neck surgery, fibromyalgia, anticoagulant use, pregnancy, or BMI > 28 kg/m². Interventions: Participants were randomly allocated to a low-intensity galvanic current group or a sham group. The active group received static percutaneous microelectrolysis with a 0.3 × 25 mm acupuncture needle and current intensities ranging from 0.12 mA to 0.6 mA (2.53 mA/cm²) for three 60-second cycles. In the sham group, the needle was inserted superficially (up to 3 mm) over the upper trapezius region without reaching the muscle, and no electrical current was applied. Objectives: 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. Materials and Methods: Pressure pain threshold (PPT) and surface electromyographic (EMG) (basal and isometric peak and RMS) were measured at baseline, 1 minute, and 10 minutes post-intervention. Independent-sample t-tests and effect sizes (Cohen’s d) were calculated (p < 0.05). Results: Sixteen participants were randomized, with eight allocated to each group. No statistically significant differences were observed between groups for PPT or EMG variables. However, medium effect sizes were observed for resting and isometric root mean square (RMS) EMG activity at 1 minute post-intervention, and a large effect size for resting peak EMG activity at 1 minute. Conclusions: In this pilot trial, no statistically significant between-group differences were observed. Although moderate-to-large effect sizes were observed for some EMG variables immediately post-intervention, these results should be interpreted cautiously. Larger trials with longer follow-up are needed.