Influence of food properties and body position on swallowing-related muscle activity amplitude.

This study was designed to examine the effect of different food properties and body positions on electromyographic amplitudes of the anterior tongue (AT) and suprahyoid (SH) muscles during swallowing in normal subjects (six men and three women; 21-30 years old). Each subject was asked to swallow three foods (consisting of 2.0%, 5.7% or 9.1% of a thickening agent dissolved in water) with different textural properties in one of four body positions: upright, inclined at 60 degrees or 30 degrees , or supine. Surface electromyograms (EMG) were recorded from the anterior tongue and SH muscles, and the integrated and cumulated EMG were used to evaluate the amplitude changes. The increases in food hardness and adhesiveness elevated the integrated and cumulated EMGs of both the AT and SH muscles during swallowing in a stepwise manner (P < 0.0001, one-way anova) that was independent of the body position. There was a linear relationship between the concentrations of the thickening agent and the logarithmic values of the food hardness. There was also a parallel relationship between the logarithmic hardness values and the final logarithmic values of the cumulated muscle activity during swallowing. Unlike these simple amplitude responses of the AT and SH muscles to the different food properties, our previous studies have shown that the durational responses of these muscle activities to different food properties are more complicated. Possible neural mechanisms responsible for the amplitude responses observed are discussed.