Influence of food properties and body posture on durations of swallowing-related muscle activities

The purpose of this study was to determine (i) whether or not textural properties of foods and body positions affect the durations of anterior tongue and suprahyoid muscle activities during swallowing, and (ii) if such changes occur, is the 'pre-peak' or the 'post-peak' duration of integrated muscle activity responsible. We used two test foods with different proprieties of hardness and adhesiveness. We recorded electromyograms (EMGs) from the anterior tongue and suprahyoid muscles as well as the laryngeal movement associated with swallowing in normal subjects (six men and three women; 21-30-years old). The subjects swallowed the test foods in four randomly set postures: upright, two inclined (60 degrees and 30 degrees to horizontal), and supine. None of the measured durations for the anterior tongue and suprahyoid EMGs were different among the four positions during swallowing of either food. The 'total' duration, from the start to the end of the integrated EMG, of anterior tongue activity was significantly (P < 0.001, ANOVA) longer during the swallowing of the tougher and more adhesive food than during swallowing of the other food, but the 'total' duration of suprahyoid activity was unchanged. The 'post-peak' duration of anterior tongue activity, which stretched from the peak to the end of the integrated EMG, was also significantly longer (P < 0.001, ANOVA) during swallowing of the tougher and more adhesive food. The results indicate that tougher and more adhesive foods prolong the duration, especially the 'post-peak' duration, of anterior tongue activity during swallowing in the upright, inclined and supine positions.