Use of suction electrodes for measurement of intrinsic tongue muscular endurance during lingual pressure generation

Background: Lingual pressure (LP) generation is cooperatively controlled not only by the intrinsic tongue (I-ton) muscles but also by hyoid muscle activation. However, the measurement of endurance and fatigue properties of I-ton muscles is difficult due to the instability of electrodes. Objective: The purpose of this study was to apply suction electrodes to measure electromyograms (EMGs) of I-ton muscle and to evaluate integrated EMG amplitude (iEMG) and mean power frequency (MPF) of EMG in the I-ton and hyoid muscles performing continuous LP. Methods: Twenty healthy adult volunteers (10 males, 10 females, mean age 28.8 years) were instructed to perform 10-s LP generation tasks at 25%, 50%, 75% and 100% of maximum LP in randomised order with visual feedback. During each task, EMGs of the I-ton, suprahyoid (S-hyo), infrahyoid (I-hyo) and masseter (Mass) muscles were simultaneously recorded. The iEMG and MPF of EMG burst during 10-s LP tasks were compared. The recording period was divided into three substages to analyse temporal changes with the Friedman test. Results: During the 10-s task, the iEMG significantly increased as the LP strength increased (p < .001). There was no time-dependent change in the I-ton iEMG; however, the MPF of the I-ton EMG burst decreased in all tasks (p < .05). The S-hyo and I-hyo iEMGs gradually increased, especially with strong LP (p < .01). Conclusion: While I-ton muscles may easily fatigue during 10-s LP generation, S-hyo and I-hyo muscles may help compensate for the weakened I-ton muscle activity by increasing their activity to maintain LP.