Electromyography analysis of upper trapezius relaxation induced by interferential current in subjects with neck discomfort

Purpose: To evaluate the muscular relaxation of the upper trapezius induced by interferential current (IFC) application during rest and functional activities using surface electromyography registration (EMG). Method: We evaluated the "root mean square" value (RMS) of the upper trapezius during rest and functional activities in subjects with neck discomfort before and after IFC applications. Thirty female participated in the study, mean age of 23.0 (±4.0) years and a body mass of 22.1 (±2.5) kg/[m.sup.2]. The subjects received three TFC applications over a 5-day period, with a frequency of 4.000 Hz, an amplitude modulated frequency (AMF) of 75 Hz, a frequency variation (AF) of 35 Hz, a slope of 1/1, a sensorial level intensity, and an application time of 30 minutes per session in the upper trapezius. Results: Repeated measures analysis of variance demonstrated significant bilateral decrease (p 0.05). Conclusion: IFC seems to induce a relaxation of the upper trapezius muscle in both medium-term analyses at rest and during functional activities. Therefore, there was not an immediate effect in the experimental model used. KEY WORDS: Electromyography, electro therapy, interferential currents, muscle relaxing, trapezius