Endurance measurement of hyoid muscle activity and hyoid-laryngeal position during tongue lift movement

Background Tongue lift movement (TLM) is used as a therapy to improve tongue pressure against the hard palate for dysphagic patients. Objective The present study aimed to characterize the time-dependent endurance changes in hyoid muscle activity and hyoid-laryngeal displacement during TLM in different ways. Methods Sixteen young healthy volunteers were instructed to perform TLM at maximum effort (100%) against the anterior and posterior parts of the hard palate using a balloon-type tongue pressure instrument, followed by a 10-second recording during anterior 80% TLM, anterior 100% TLM, posterior 80% TLM and posterior 100% TLM with visual feedback. Electromyography (EMG) of suprahyoid (S-Hyo) and infrahyoid (I-Hyo) muscles and videofluorography were simultaneously recorded. To evaluate temporal changes, the recording period was divided into three substages: early, middle and late. Tongue pressure, integrated EMG (iEMG), power frequency of EMG burst and hyoid-laryngeal position were compared among the conditions (80% vs 100%, anterior vs posterior and early vs middle vs late). Results Tongue pressure was stably maintained for 10 seconds in all conditions. S-Hyo iEMG and I-Hyo iEMG were significantly greater at 100% than at 80%, while no significant difference was observed between positions. S-Hyo iEMG and I-Hyo iEMG significantly increased at the late stage, while power frequency of EMG burst gradually decreased. Significant temporal changes in laryngeal elevation were observed only in posterior 100% TLM. Conclusion The current results suggested that isometric posterior TLM may be more useful compared with anterior TLM in clinical situations for dysphagic patients to elevate the hyolaryngeal complex.