Abstract
To assist in developing a “normal” electromyographic (EMG) envelope, various amplitude normalization procedures for surface EMG signals have been used to reduce the inter- and intrasubject variability of collected data. The effect of two normalization methods (normalization to mean ensemble average: NME, and peak ensemble average: NPE) on intersubject variability and reproducibility of surface EMG profiles from masticatory muscles during unilateral gum chewing was examined. The EMG profiles for anterior temporal (Ta), posterior temporal (Tp), masseter (M) and anterior belly of digastric (Da) muscles on chewing side from 5 asymptomatic dentate subjects were made on 3 different sessions. Coefficients of variation and intraclass correlation coefficients, ICC (3, 1), were used to assess the variability and reproducibility. Each normalization procedure reduced the intersubject variability of unnormalized EMG profiles for Ta, Tp and M. NME procedure provided lower intersubject variability for Da. Reproducibility of unnormalized profiles for Ta, Tp and M was significantly improved by the two procedures. The NME procedure on Da was more reproducible than the NPE procedure. These results showed that phasic characteristics of muscular activity influenced the outcome of amplitude normalization. These methods used. were reliable and reproducible for measuring phasic muscle activity of masticatory muscles during gum chewing.
