Power spectra analysis of levator veli palatini muscle electromyogram during velopharyngeal closure for swallowing, speech, and blowing.

The velopharynx closes during swallowing and pneumatic activities. Pneumatic closure, which is acquired, prevents expiratory air from passing into the nasal cavity, whereas during swallowing, velopharyngeal closure is achieved innately, preventing regurgitation into the nasal cavity. These findings suggest that velopharyngeal closure during swallowing is a different mechanism from that during pneumatic activity. The purpose of this study was to clarify activity differences of the levator veli palatini muscle during swallowing, speech, and blowing using power spectra analysis. Five normal adults served as subjects. Each subject was instructed to speak, blow, and swallow. Electromyograms of the levator muscle were recorded and the spectrum analyzed for each task to calculate the mean power frequency (MPF) of EMG signals. There was no significant difference in MPF between speech and blowing for all subjects. MPF was significantly greater during swallowing than during pneumatic activities for all subjects. The MPF value can reflect the composition of active motor units during muscle contraction. It was therefore indicated that the motor units of the levator muscle participating in contraction were different during swallowing and respiratory activities.