Effects of the Head Lift and Recline Exercise Regimens on the Neuromuscular Control of Functional Swallowing in Older Adults: An Electromyography Study Revealing Potential Differential Mechanisms.

Purpose: The head lift exercise (HLE) and recline exercise (RE) are rehabilitative exercises that have been shown to elicit similar biomechanical swallowing changes in older adults. However, the neuromuscular mechanisms underlying these changes are unknown and could elucidate the physiological mechanisms these exercises target.

Method: A randomized clinical trial with two arms-a 6-week HLE or RE regimen-was conducted. Data were collected on older adults pre- and posttreatment and at 6-week follow-up using videofluoroscopic swallow studies (VFSSs) and surface electromyography (sEMG). Results of the VFSS showing similar hyolaryngeal excursion gains post both regimens have been published. This follow-up study presents the sEMG data and includes data from 18 older adults (age range: 60-82 years; HLE = 9, RE = 9) from the pre- and posttreatment time points. sEMG activity measures (normalized mean amplitude, burst duration, and time to peak sEMG amplitude) were collected from submental muscles during standardized swallow tasks.

Results: Normalized mean amplitude, burst duration, and time to peak amplitude during swallowing did not significantly change posttreatment for either group. Post hoc correlational analysis of percent change between outcome measures from pre- to posttreatment revealed a strong negative relationship between normalized mean amplitude and time to peak amplitude for liquids (r = -.926, p = .0001) and pudding (r = -.901, p = .0001), indicating that participants who required greater levels of muscular contraction to functionally swallow posttreatment may need less time to reach that contraction level and vice versa.

Conclusions: In combination with the Fujiki, Oliver, Malandraki, et al. (2019) results, these findings support that older adults show improvements in anterior and superior hyoid excursion post both HLE and RE without the need for greater submental musculature contraction. The inverse relationship identified post hoc between the percent change of amplitude and time to peak amplitude may indicate different neuromuscular mechanisms for biomechanical gains and needs further exploration for future personalized treatments.