Properties of hyoid muscle contraction during tongue lift measurement.

Abstract

Tongue lift movement (TLM) task is considered a treatment strategy in dysphagic patients. However, there is no evidence of effect of sustained tongue movements on the related muscle contraction. The present study aimed to characterise the properties and time-dependent changes of the electromyographic (EMG) features of suprahyoid muscles during TLM. Twenty young healthy volunteers were instructed to perform TLM at maximum effort in either the anterior or the posterior position, during measurement of tongue pressure for 7s. Supra- (S-hyo) and infra-hyoid (I-hyo) EMGs were recorded. The area and power frequency of EMG burst and the area under the curve of tongue pressure were compared among the conditions: trials (1st, 2nd vs 3rd trials); anterior vs posterior TLM; and early vs late 3s of each trial. There was no difference in the tongue pressure among trials or between the early and late 3s. Anterior tongue pressure was significantly higher than posterior tongue pressure (P<.001). The area of I-hyo EMG burst was significantly larger (P=.044), and the power frequency of I-hyo EMG burst was significantly smaller (P=.042) during posterior TLM than anterior TLM. A significant difference in the power frequency of both EMG bursts was observed between early and late stages during both anterior (P<.05) and posterior (P<.01) TLM. Hyoid muscles may compensate for rapid fatigue of the tongue muscle to maintain tongue pressure by changing their activity pattern during tongue pressure generation.