Effects of the eccentric chin closure exercise on submental muscle activation, muscle strength, dysphagia limit, perceived exertion and pain in healthy volunteers: A prospective, randomized parallel group study.

Objective(s): Eccentric Chin Closure (ECC) exercise is a model designed to strengthen the suprahyoid muscles, aligned with the principles of eccentric exercise and the characteristics of these muscles. This study aimed to investigate the effects of the ECC exercise on submental muscle activation, muscle strength, dysphagia limit, perceived exertion, and pain, in comparison to the Shaker and Chin-Tuck Against Resistance (CTAR) exercises.

Methods: In this parallel randomized controlled trial, for the initial assessment fifty-four healthy volunteers aged between 19-28 years with submental activations were recorded during the isotonic components of the Shaker, CTAR, and ECC exercises using surface electromyography. After the initial assessment, the volunteers were randomized to the Shaker, CTAR, and ECC exercise groups with 18 volunteers each group, and followed an 8-week exercise program. Maximum voluntary isometric contractions (MVC), muscle strength, dysphagia limit, perceived exertion, and pain were recorded at baseline in 4th week and 8th week.

Results: At the initial assessment, lower submental muscle activation was observed during the Shaker exercise (p<0.05). Follow-up measurements demonstrated that the eight weeks of exercise was effective in increasing MVC activations and muscle strength across all groups. Considering the group*time effect, CTAR (0.36 ± 0.10) and ECC (0.40 ± 0.14) exercises were found to be more effective in increasing MVC than the Shaker (0.29 ± 0.19) exercise (F = 7.203, p<0.001), and the ECC (32.87 ± 6.55) exercise was more effective in improving muscle strength than both the Shaker (26.03 ± 5.86) and CTAR (27.95 ± 6.33) exercises (F = 6.786, p<0.001). Perceived exertion (F = 1.044, p = 0.388) and pain scores (F = 0.346, p = 0.846) showed statistically similar changes across the Shaker, CTAR, and ECC exercise groups.

Conclusion: The ECC exercise demonstrated similar effects on MVC to CTAR, but resulted in greater MVC than the Shaker exercise among healthy volunteers at 8 weeks. ECC was also more effective compared to Shaker and CTAR in terms of strength gain, with all exercises showing comparable levels of perceived exertion and pain.