Effect of Systematic Effortful Swallowing Exercise on the Activation Level of the Submental Muscles and Tongue Strength in Older Adults

Introduction: Effortful swallowing (ES) is known to significantly increase the activity of the submental muscles, including the suprahyoid muscles, which play an important role in elevating the hyoid bone and larynx during swallowing and contributing to the opening of the upper esophageal sphincter. However, inconsistent results have been reported regarding the long-term effects of ES exercise in increasing the submental muscle activity. Therefore, this study aimed to investigate the effect of a 6-week systematic ES exercise program on the activation level of the submental muscle and tongue strength. Methods: The study included 31 healthy older adults (mean age, 75.4 ± 4.68 y; range, 65–82 y). The exercise consisted of 10 repetitions per set, wherein one session comprised 7 sets. In sets 1–3, gradual isometric tongue pressing exercises of 60%, 80%, and 100% were performed based on the maximal isometric pressure (MIP) of the posterior oral tongue; in sets 4–7, gradual swallowing exercises were performed at 60% and 80% intensities. Resistance and biofeedback were provided to the posterior oral tongue during exercise using Iowa Oral Performance Instrument (IOPI). Each session lasted 30 min, and the exercise was performed twice a week for a total of 6 weeks. The effects of exercise on submental muscle activity (measured using surface electromyography) and tongue pressure-related variables (measured using IOPI) were verified using paired t tests at baseline and week 7. Results: After 6 weeks of strengthening exercise, the maximal activity of the submental muscles during ES, anterior and posterior oral tongue MIP, typical swallowing and ES pressure, and posterior oral tongue endurance significantly increased compared to those at baseline (p < 0.05). Conclusion: The ES exercise program, which was structured by systematically adopting exercise principles related to strength training, significantly improved the swallowing-related muscle strength of healthy older adults. It is suggested that this effect was caused by systematic warm-up exercises applied prior to performing strengthening exercises for swallowing-related muscles, resistance and biofeedback provision using IOPI during main exercise, and provision of sufficient rest time between sets. Further research is needed to systematically examine the effects of variables related to the composition of exercise programs.