Korean J Pain.  2025 Apr;38(2):187-197. 10.3344/kjp.24332.

Effectiveness of intramuscular electrical stimulation using conventional and inverse electrode placement methods on pressure pain threshold and electromyographic activity of the upper trapezius muscle with myofascial trigger points: a randomized clinical trial

• Shanmugam S
• dos Anjos FV
• Sá Ferreira Ad
• Muthukrishnan R
• Kandakurti PK
• Durairaj S

• KMID: 2566650
• DOI: http://doi.org/10.3344/kjp.24332

Abstract

Background
This study investigates whether intramuscular electrical stimulation (IMES) with inverse electrode placement (IEP) or conventional electrode placement (CEP) more effectively modulates pain. The current study’s aim was to compare the effects of IMES using IEP and CEP, and sham-IMES on the pressure pain threshold (PPT), EMG activity, upper trapezius (UT) muscle length and pain severity among adults with UT myofascial trigger points (MTrPs).
Methods
Thirty-six male adults with UT-MTrPs were allocated into three groups. IEP, CEP and sham groups were respectively treated with a single IMES session using IEP, CEP, and sham-IMES. Pain intensity, PPT, EMG activity (root mean square, RMS) and UT muscle length were measured on day one before the treatment, day one post treatment and at a day three follow-up to determine the immediate and short-term effectiveness of IMES.
Results
IMES using both IEP and CEP methods produced significant higher changes in UT-PPT (median, interquartile-interval, IEP group: 3.25, 2.56–3.50 and CEP group: 2.75, 1.75–3.00, vs. sham group: 1.07, 0.89–1.71 kg/cm 2 ), RMS (IEP: 0.31, 0.26–0.35 and CEP: 0.36, 0.23–0.38, vs. sham: 0.21, 0.16–0.25 mV), and UT muscle length (IEP: 9.50, 8–12.75 and CEP: 8, 7–10, vs. 1.5. 1–2.75 degrees) and UT-pain severity (IEP: 3.00, 2.25–4 and CEP: 3, 3–3, vs. sham: 2, 2–2.75 points on VAS) compared to the score change in sham-IMES at day three follow up.
Conclusions
Pain modulation can be effectively achieved using IMES regardless of electrode placement method, with different electrode configurations.

Keyword

Electric Stimulation; Electromyography; Muscles; Skeletal; Neck Pain; Pain Measurement; Pain Threshold; Shoulder Pain; Trigger Points