Effects of oropharyngeal exercises / myofunctional therapy on orofacial function and corticomotor excitability in healthy individuals – implications for obstructive sleep apnea?

Oropharyngeal exercises / myofunctional therapy (OE/MT) offer complimentary beneficial effects on obstructive sleep apnea. However, the complex nature of intervention impedes the understanding of underlying mechanisms related to sensorimotor function and corticomotor control of involved muscles. This study explored the sensorimotor rehabilitation effects of OE/MT tasks in twenty-two healthy adults (24.1 ± 3.1 years) using a cross-over design to better understand the normal physiology of tongue before and after these different tasks. Sessions involved breathing training (BT), tongue training (TT), or a no-training control (CT). Transcranial magnetic stimulation (TMS) evaluated motor-evoked potentials (MEPs) of the tongue and first dorsal interosseous (FDI, internal control) muscles before and after each session. Secondary outcomes included orofacial muscular pressure/force, peak expiratory flow rate (PEFR), oral stereognosis ability, and subjective ratings. Results showed TT significantly increased tongue MEP amplitude (P < 0.001) and volume (P < 0.001) compared to BT and CT. Conversely, FDI MEPs were unaffected by any task (P > 0.050). No significant differences were observed in orofacial pressure, PEFR, stereognosis, or subjective ratings (P > 0.050). These findings demonstrate that TT elicits unique corticomotor plasticity in tongue motor control, supporting the therapeutic potential of OE/MT. BT may need further development and be tested longer before functional effects can be observed.