Incomplete Swallowing and Retracted Tongue Maneuvers for Electromyographic Signal Normalization of the Extrinsic Muscles of the Larynx

Summary Purpose To investigate which muscular maneuvers provide larger electric activity (EA) of the suprahyoid (SH) and infrahyoid (IH) muscles to be used as surface electromyography (SEMG) signal normalization reference. Methods The electrical potentials of the SH and IH muscles of 12 subjects were evaluated using six muscular maneuvers, involving the position of the tongue and effort. It was selected as maximum voluntary sustained activity maneuver, the one having the minor coefficient of variation and the smallest value for each muscle group. The EA signal was converted using the root mean square in microvolts. It was considered then the maximum signal of each maneuver as the difference between the mean of three measures and the resting potential. Results The maneuvers that provided higher mean potentials with minor coefficient of variation and smallest P value were incomplete swallowing (IS) with effort (mean potential equal to 56.73 ± 8.68 with coefficient of variation of 15.30%) in SH group, and tongue retracted with mouth open (TROM, mean potential equal to 46.57 ± 7.83 with coefficient of variation of 16.81%) in IH group. Conclusion The IS with effort and TROM maneuvers should be considered for signal normalization in these muscles, respectively, and may provide conditions for using the SEMG in voice clinic. Significance The use of normalization standards in researches of SH and IH muscles in the voice area will allow comparisons among future works.