Deglutitive tongue force modulation by volition, volume, and viscosity in humans

Background/Aims Deglutitive tongue biomechanics are complex, involving bolus containment, loading, and propulsion. This study aimed to quantify the modulation of deglutitive pulsive and clearing tongue forces in varied swallowing conditions. Methods Oropharyngeal pressure and force were recorded using sensing bulbs and strain-gauge manometry in 8 volunteers during swallows of varied volume and viscosity. Volitional modulation was explored with forceful and attenuated swallows. Results Temporal analysis confirmed that bulb recordings corresponded to tongue pulsive force, and the strain-gauge recordings measured tongue clearing pressure. Volition was the most potent modifier of both tongue pulsive force and clearing pressure with values showing a fourfold increase from attenuated to forceful swallows. Bolus viscosity also induced an increase of tongue pulsive force and clearing pressure by the oral tongue. Volitional control as well as adaptation to viscosity was greatest on the anterior and middle part of the oral tongue. There was no force adaptation with increased bolus volume. Conclusions Tongue pulsive force and clearing pressure during swallow showed substantial modulation for bolus viscosity that can be reproduced by volitional control. The anterior two thirds of the tongue showed both greater forces and greater modulation than did the tongue base.