Tongue Pressure Production and Submental Surface Electromyogram Activities During Tongue-Hold Swallow with Different Holding Positions and Tongue Length.

Our previous study regarding the tongue-hold swallow (THS) demonstrated that the tongue-to-palate contact during THS could be influenced by the maximum tongue protrusion length (MTPL) of individual subjects, resulting in two different patterns of pressure generation. The present study further analyzed the influence of MTPL on the tongue pressure production along with submental surface electromyography (sEMG) during THS, in order to establish an index to better control THS effects. Tongue pressure using a sensor sheet system and concurrent submental sEMG activities were measured during swallowing tasks in 18 healthy young adults. Task conditions comprised THS at two different degrees of tongue protrusion and dry swallow. Tongue pressures and sEMG activities were compared among three task conditions, and correlations of MTPL with tongue pressure were also investigated. Additionally, a ROC curve was used to find a cut-off value for MTPL to predict changes (increases and decreases) in tongue pressure during THS. The duration and the amount of submental muscle activity increased concurrently during THS. Two trends were shown on the change in tongue pressure at the posterior-circumferential part of the hard palate during THS compared to dry swallow; the maximal magnitude and the integrated value of tongue pressure increased in some subjects, while these values decreased in others. Thirty-two millimeters was found to be the cut-off value of MTPL, which distinguishes increase/decrease pattern of tongue pressure with sensitivities of 60.0-85.7%. The present finding suggests that more reliable THS effects should be attainable using MTPL to set the tongue-hold position.