Activity patterns of the suprahyoid muscles during swallowing of different fluid volumes

Summary Influences of bolus volumes on activity patterns of the suprahyoid muscles during swallowing were examined using the T_P technique (which quantitatively evaluates muscle activity patterns and indicates a negatively skewed pattern at lower T_P values) in healthy young adults (eight men and four women). One of six volumes of tea ranging from 10 to 32 mL was delivered randomly to each subject while recording an electromyogram of the suprahyoid muscles and a laryngeal mechanogram with a piezoelectric sensor. Each subject was asked to swallow the full volume of liquid in a gulp if possible. T_P values were calculated as deciles from T₀ to T₁₀₀ during intervals that were defined by the trajectory of the laryngeal mechanogram recorded during swallowing. Seven significant differences were detected in the average T_P values from T₃₀ to T₆₀: between 16 mL (e.g., 0·448 in T₃₀) and 25 mL (0·408 in T₃₀) and between 20 mL (0·453 in T₃₀) and 25 mL. There were significant differences among the 12 subjects for all of the nine average T_P values (Ps < 0·001), suggesting a notable intersubject variation in the suprahyoid (SH) activity patterns. The average peak amplitudes of the integrated suprahyoid activity differed significantly among the six volumes (P < 0·001), while the average durations measured by the laryngeal mechanogram did not. The present results suggest that the swallowing volume mainly affects SH activity patterns, which were evaluated by the T_P technique, during the early period of each swallow.