Levator veli palatini muscle activity in relation to intraoral air pressure variation.

The purpose of this investigation was to study the operating range of the levator veli palatini muscle for a nonspeech task (blowing) and to determine where in that range levator activity for speech lies. Ten adult subjects without speech or velopharyngeal abnormalities participated. Levator EMG activity for speech occurred in the lower region of the total range for blowing. In two subsequent experiments involving a subset of 4 subjects, it was found that overall effort may have had a small effect on levator activity apart from its role in velopharyngeal closure for aerodynamic purposes. The results of the main experiment are discussed in relation to the concept of threshold of fatigue as it may influence velopharyngeal control mechanisms.