Technical Parameters in Surface Electromyography for Voice and Muscle Tension Dysphonia: A Scoping Review

Muscle tension dysphonia is characterized by excessive laryngeal and extralaryngeal muscle tension, yet current objective voice assessments may not directly quantify this hallmark feature. Surface electromyography (sEMG) has emerged as a noninvasive method for measuring extrinsic laryngeal muscle activity, but its clinical and research utility is limited by inconsistent technical parameters across studies, which prevents comparisons across studies and hinders protocol standardization.

Following the PRISMA Extension for Scoping Reviews guidelines, this review examined the technical parameters employed in sEMG research involving vocalization. Included papers involved a participant wearing an sEMG device, described the placement of the sEMG device, and incorporated a vocalization component.

From 1428 potential studies, 77 were included. Across these studies, sEMG was used in a broad range of voice, speech, and singing experiments. Electrode placements were most commonly reported as anterior neck, perilaryngeal, submental, suprahyoid, infrahyoid, sternocleidomastoid, and orofacial regions. Across studies, outcome measures included mean sEMG amplitude, root mean square values, normalized electrical activity, percentage of maximum voluntary contraction, peak sEMG values, frequency-domain features, coherence measures, muscle network measures, and classifier performance metrics.

The results support sEMG as a noninvasive method for studying extralaryngeal and perilaryngeal muscle activity, but current evidence is limited by methodological heterogeneity. The literature remains limited by a lack of standardized protocols for electrode placement, task selection, normalization, and outcome reporting.