The purpose of this study was to examine whether the palatoglossus (PG) muscle is involved in the regulation of function during the transition from the oral to the pharyngeal phase. Seven normal adults participated in the study. Smoothed electromyography (EMG) signals of the PG muscle and levator veli palatini (LVP) muscle were collected. Each subject swallowed water at five different volumes: 12.5%, 25%, 50%, 100%, and 150% (or 200%) of his/her optimum swallowing volume. PG muscle waveform showed two patterns of activity: one of a single peak and the other of two peaks. There was no significant difference (p < 0.01) in the timing of emergence between the single peak and the second peak of the two-peak pattern. There were two patterns of PG muscle activity in response to a change in swallowing volume, i.e., one was a pattern in which the activity was correlated to the change in swallowing volume, the other was a pattern in which the activity was not changed but almost at the maximum activity level, irrespective of swallowing volume. We conclude that the PG muscle could be involved in the regulation of swallowing from the oral to the pharyngeal phase. The activity could be influenced by swallowing volume.

The aim of this study was to examine whether the levator veli palatini (LVP) muscle might be involved in the regulation of velopharyngeal function during the transition between the oral and pharyngeal phases during swallowing, and to examine whether LVP muscle activity could be regulated in relation to the volume of swallowing. Eight normal adults participated in this study. Smoothed EMG signals of the LVP muscle were collected. At the same time, palatoglossus muscle activity was also monitored. Each subject swallowed water at five different volumes: 12.5%, 25%, 50%, 100%, and 150 (or 200) % of the optimum volume for swallowing, which was individually determined for each subject. LVP muscle activity was positively correlated with changes in swallowing volume. The LVP muscle was involved in the regulation of swallowing during the transition from the oral to pharyngeal phases.

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.

It has been reported that the levator veli palatini muscles of speakers with velopharyngeal incompetence tend to demonstrate muscle fatigue during speech. This study examined whether a speech aid prosthesis might reduce levator muscle fatigue in such speakers. Eight individuals with post-surgical cleft palates, and who wore a speech aid prosthesis, were studied. Each person was asked to pronounce the syllable [pu] more than 50 times. Mean power frequency (MPF) of one syllable was obtained from electromyographic data from the levator muscle. The MPF regression line was calculated during the course of syllable repetition. The absolute values of the slopes of the regression lines with the prosthesis were significantly smaller than those without the prosthesis. It was shown that the prosthesis reduced the decrease in MPF during speech. These results suggested that speech aid prostheses reduce levator muscle fatigue during speech in persons with velopharyngeal incompetence.