Abstract
Purpose The main objective of this study was to investigate the effect of time of contraction and rest on the masseter and temporal muscles activity. Methods 49 female subjects between 18 and 30 years of age were divided into TMD (n: 26) and control groups (n: 23). Surface electromyograph was used to evaluate the anterior temporal and masseter muscles during contraction and rest protocols. The root means square, median frequency and slope coefficient of the linear regression line parameters were analyzed. Results A significant effect of time in the contraction and rest muscle protocols was found. TMD patients showed a significant decrease in median frequency in the right masseter muscle and the slope coefficient in the right temporal muscle during the contraction protocol to control subjects. Conclusion Despite the TMD patients presented with higher fatigue susceptibility compared to the control group, both groups must meet the maximum time of 5 s of maximum voluntary contraction and at least 30 s rest between successive contractions of masticatory muscles during clinical or research assessment protocols.
Highlights
Temporomandibular disorders (TMD), called craniomandibular dysfunction (CMD), is a broad term that includes several clinical manifestations involving the temporomandibular joint and associated structures
The median frequency (MF) (%), root mean square (RMS) (%), and the slope coefficient of MF and RMS for each muscle and period of contraction protocol (CP) and rest protocol (RP) are shown in Figures 2, 3 and 4, respectively, for both TMD and control groups
RMS and MF values were calculated for all periods over 1000 initial data
Summary
Temporomandibular disorders (TMD), called craniomandibular dysfunction (CMD), is a broad term that includes several clinical manifestations involving the temporomandibular joint and associated structures. Emotional stress and muscle tension contribute and aggravate the TMD and can difficult its recovery[1]. Evidence shows that myofascial pain is related to muscle hyperactivity[3,4] and to alterations in the muscle motor behavior during the function of mastication. Subjects with TMD present with more asymmetry during mastication[5,6] and larger amplitude of muscle activity during rest position[7,8,9]. TMD patients have larger amplitude of muscle activity because of its lower functional efficiency and predisposition to muscle fatigue when compared to asymptomatic subjects performing the same activity[7]
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