Explorative Investigation of Masticatory and Submental Muscles Activity in Experimentally Induced Oral Motor Tasks in Young Healthy Individuals

AIM: To explore the activity of the temporalis (TM), masseter (MM) and submental (SM) muscles using standardised surface electromyography (ssEMG) during four functional tasks: clenching, saliva, pacifier-induced and thumb sucking-induced swallowing in young healthy individuals, additionally assessing the duration of TM, MM and SM activity and symmetry during the three different swallowing tasks. METHODS: ssEMG data of TM, MM and SM were collected during the above-mentioned four functional tasks in 27 volunteers (13 women; mean age 22.7 ± 1.78 years). The duration of activity of each muscle during the three swallowing conditions was recorded by measuring their activation time. Repeated measures ANOVA followed by Tukey's post hoc test was used for statistical analysis to compare muscle activity during different functional tasks. RESULTS: Clenching led to marked TM and MM activity compared to all swallowing conditions (p < 0.001). When comparing swallowing tasks, thumb sucking showed significantly longer activation times (p < 0.05) and greater SM recruitment (p < 0.05) than both saliva and pacifier-induced swallowing. TM and MM activity did not differ between the different swallowing conditions. SM showed consistently higher activation symmetry than TM (p < 0.01) and MM (p < 0.05) across all tasks. Clenching also elicited a more symmetrical activation pattern than any of the swallowing tasks (p < 0.001). CONCLUSION: Clenching is the most demanding task in terms of both muscle activity and activation time. Experimentally induced non-nutritive swallowing conditions were associated primarily with increased submental muscle activity and prolonged activation times across all muscles compared with physiological swallowing.