Abstract

The study of muscle activity as a function of vertical dimension has been extensively developed in the field of oral physiology. It involves asking subjects to open their mouths to a predetermined distance and then recording muscle activity in that position. Most studies perform this without accounting for physiological differences among patients. The objective of this study is to present a protocol for recording muscle activity at various mouth-opening levels using electromagnetic articulography (EMA) and surface electromyography (sEMG), normalizing opening degrees and muscle activity. Muscle activity recordings were obtained in the position of maximum intercuspation and maximum mouth opening. Based on these recordings, the position corresponding to 5–50% of maximum opening was calculated. EMA and sEMG recordings were performed at these levels. Muscle activity during maximum voluntary clenching was recorded and used to normalize the previous data. In all cases, three 5-second recordings were obtained. The analysis of muscle activity using EMA and sEMG did not present any complications. A slight difference was observed between the intended percentage of mouth opening and the actual percentage achieved. The method described in this study is a tool that allows for the analysis of muscle activity at various mouth-opening levels in a way that has not been previously explored in the literature. © 2025 by the authors.