ABSTRACT
Purpose
To verify the electrical activity of the orbicularis oris in four different isometric tasks and to indicate the most appropriate task for use as a reference in the normalization of the electrical signal of the orbicularis oris muscle by maximum voluntary contraction.
Methods
Twenty-two individuals participated in the study, of which 10 were male and 12 were female, with ages ranging from 20 to 33 years. The electrical activity of the upper and lower parts of orbicularis oris muscle was recorded during the following isometric tasks: lip protrusion with bilabial closure; lip protrusion without bilabial closure; the counter resistance using the plate of labial resistance and lips prehension. The order of the tasks was randomized among participants. Data were compared between tasks for each lip part.
Results
in the upper marginal segment, the task with the highest mean and median amplitude was lip prehension, although there was no significant difference between tasks. The lowest coefficient of variation was obtained in the counter resistance task with the plate of labial resistance. In the lower marginal segment, the task with the highest mean and median amplitude was labial protrusion with lips closure, which also had the lowest coefficient of variation. In this segment, there was a significant difference between labial protrusion with lips closure and prehension, with the highest values obtained in the first task.
Conclusion
lip protrusion with bilabial closure is suggested as reference for the normalization of the electrical signal of the orbicularis oris muscle, by maximum voluntary contraction.
Keywords:
Masticatory muscles; Orbicularis muscle of the mouth; Facial muscles; Isometric contraction; Electromyography; Rehabilitation
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