Surface EMG frequency dependence on force in the masseter and the anterior temporal muscles.
Myoelectric power spectrum analysis was used to study isometric contractions, 10-15 s long, of the masseter muscles and the anterior temporal muscles. Surface EMG activity was recorded from these muscles for nine females while biting on a bite force transducer up to maximal effort (100% maximal voluntary contraction; MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses were made of MF versus bite force (0-100% MVC). The mean MF values of all females' masseter muscles increased up to 55-60% MVC. For the anterior temporal muscles no increase in mean MF was found above 20-25% MVC. The increase in MF was possibly dependent on recruitment of type I fibers and low-pass tissue filtering effects. The slope of regression for the force level 0-60% MVC was intraindividually steeper for the masseter muscles than for the anterior temporal muscles. A similar decrease in mean MF was found for the masseter muscles and the anterior temporal muscles for the force level 60-100% MVC. The possibility of muscular fatigue was discussed.
Hagberg
C
C
Department of Orthodontics, Karolinska Institute, Huddinge, Sweden.
Hagberg
M
M
D000328:Adult; D001732:Bite Force; D003766:Dental Occlusion; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008406:Masseter Muscle / Q000502:physiology*; D008410:Masticatory Muscles / Q000502:physiology*; D009119:Muscle Contraction; D013314:Stress, Mechanical; D013703:Temporal Muscle / Q000502:physiology*