EMG activity of orbicularis oris superior, orbicularis oris inferior, and masseter muscles of articulatory disordered children.

The peak amplitude of EMG activity was measured from the orbicularis oris superior ( OOS ), orbicularis oris inferior ( OOI ) and masseter muscles for 8 normal and 8 articulatory disordered children, and 8 normal adults repeating/p ae/ at a fast rate. The three groups of subjects evidenced similar levels of average peak EMG activity across the three muscles; however, the articulatory disordered children exhibited less than normal variance for the OOI while the variability of performance of OOS and masseter muscles were similar to the normal speakers'. These data were interpreted as reflecting a limited degree of flexibility in the control of certain articulators that may affect the disordered children's ability to compensate during speech.