Effect of a repeated jaw motor task on masseter muscle performance.
OBJECTIVE
The aim of this study was to investigate the effects of 5-days repeated jaw-motor tasks on masseter muscle accuracy performance.


METHODS
Sixteen healthy participants performed a tooth-clenching task (TCT) of 58-minutes on five consecutive days. During measurements, electromyography (EMG) of both masseter muscles was recorded. Each day, the 100% maximum voluntary contraction (MVC) level was determined before the TCT. In the first and third TCT series, participants were instructed to target force levels without visual feedback. During the second TCT series, visual feedback on muscle activity level was displayed. One series consisted of three force levels (10%, 20%, and 40% MVC). In the series, participants alternated between a 30-s rest-block and a 30-s task-block for 360 s. In the task-block, participants alternated between a 5-s rest-block and a 5-s task-block. EMG activity during epochs of 5-s was quantified by calculation of the root-mean-square (RMS) values. To evaluate the accuracy of the performance, the coefficient of determination (CD) of the target force level-EMG curve was calculated from all series.


RESULTS
No significant day-to-day differences in EMG RMS amplitudes were observed during MVC. CDs differed significantly between the five days (P<0.001). CDs in the first series on day 1 were significantly lower than CDs in the first series on days 4 and 5 (P<0.05).


CONCLUSIONS
The findings suggest that a rigorous training paradigm may improve the performance of masseter muscles in terms of accuracy but not MVC. This might have implications for understanding the rehabilitation of patients with functional disorders in the stomatognathic system.
Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan; Section of Clinical Oral Physiology, Department of Dentistry, Aarhus University, Denmark. Electronic address: iida.takashi96@nihon-u.ac.jp.
Takashi
T
Iida
Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan.
Osamu
O
Komiyama
Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan.
Hisae
H
Honki
Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan; Section of Clinical Oral Physiology, Department of Dentistry, Aarhus University, Denmark.
Yoshihiro
Y
Komoda
Section of Clinical Oral Physiology, Department of Dentistry, Aarhus University, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON), Denmark.
Lene
L
Baad-Hansen
Department of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japan.
Misao
M
Kawara
Section of Clinical Oral Physiology, Department of Dentistry, Aarhus University, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON), Denmark; Department of Dental Medicine, Karolinska Institute, Huddinge, Sweden.
Peter
P
Svensson
D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography / Q000379:methods; D056228:Feedback, Sensory / Q000502:physiology; D005260:Female; D006801:Humans; D007568:Jaw / Q000502:physiology*; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D055815:Young Adult
EMG; Masseter muscle; Motor learning; Tooth clenching