Effect of experimental jaw-muscle pain on mastication: Differential patterns of electromyographic activity in jaw and neck muscles

• Published in: Journal of electromyography and kinesiology 2016
• Main Authors: Pasinato, Fernanda, Santos-Couto-Paz, Clarissa C, Luis Lopes Zeredo, Jorge, Bruzadelli Macedo, Sergio, C. R. Corrêa, Eliane
• Format: Article
• Language: English
• Subjects: Physical Medicine and Rehabilitation
• ISSN: 1050-6411
• DOI: 10.1016/j.jelekin.2016.09.007

Abstract The aim of this study was to verify the effects of induced masseter-muscle pain on the amplitude of muscle activation, symmetry and coactivation of jaw- and neck-muscles during mastication. Twenty-eight male volunteers, mean age±SD 20.6±2.0 years, participated in this study. Surface electromyography of the masseter and sternocleidomastoid (SCM) muscles was performed bilaterally during mastication of a gummy candy before and after injections of monosodium glutamate solution and isotonic saline solution. As a result, we observed a decrease in the amplitude of activation of the masseter muscle on the working side (p=0.009; d=0.34) and a reduction in the asymmetry between the working and the balancing side during mastication (p=0.007; d=0.38). No changes were observed either on the craniocervical electromyographic variables. In conclusion, experimentally induced pain reduced the masseter muscle activation on the working side, thereby reducing the physiological masseters’ recruitment asymmetry between the two sides during mastication. No effects on SCM activity were detected. These results may partly explain the initial maladaptative changes underlying TMD conditions.