The recording and analysis of EMG and jaw tracking. I. The recording procedure.

A computer-based system is described which records and analyses electromyographic (EMG) signals and tracking data for mandibular movements during function. EMG signals were obtained bilaterally from six muscles and a Sirognathograph monitored the position of the lower incisor teeth in three dimensions. Directed jaw movement tasks by subjects were monitored. These data were continuously sampled at a rate of 1 KHz per channel over an operator controlled period. Analysis of the data was performed off-line following the experiment. Individual chewing cycles associated with masticatory function were identified and the timing and dimensions of each chewing envelope established. Corresponding EMG values were also determined and displays of EMG and jaw movement were plotted on a common time base. An average chewing cycle and correlated EMG activity could also be displayed on a high resolution monitor and plotted for a hard copy to enable a comparison to be made between subjects with and without jaw dysfunction.