Tongue-hold swallow (THS) is a therapeutic maneuver that helps increase the posterior pharyngeal wall motion during swallowing (Fujiu and Logemann 1996; Lazarus et al. 2002). It has been surmised that this technique can improve the contact between the tongue base and the pharyngeal wall by increasing the pharyngeal wall contraction during swallowing (Fujiu-Kurachi et al. 2014). Fujiu and Logemann (Fujiu and Logemann 1996) reported that young healthy male adults exhibited a greater increase in anterior bulge of the posterior pharyngeal wall during THS as compared to their swallows without this maneuver. Lazarus et al. (Lazarus et al. 2002) identified that patients with head and neck cancer exhibited a significantly greater increase in duration of contact and pressure of the base of tongue to the posterior pharyngeal wall during THS as compared to their swallows without this maneuver. In addition, THS has been known to result in an increase in suprahyoid muscle contraction. Hammer et al. (Hammer et al. 2014) compared the effects of three variations of THS—saliva swallowing without any maneuver, with the tip of the tongue at the lip, and with the universal tongue-hold maneuver—using hook-wire intramuscular electromyography. In their study, healthy subjects exhibited a greater increase in the magnitude and duration of suprahyoid, genioglossus, and superior pharyngeal constrictor muscle activity during saliva swallowing with the tip of the tongue at the lip and with the universal tongue hold maneuver as compared to saliva swallowing without any maneuver.
The effect of THS likely depends on the overload principle, similar to that with general strengthening exercises. The principle of overload holds that, in order to increase the force-generating ability of a muscle, that muscle must be taxed beyond its current capacity to respond. That is, it must be exposed to a load greater than it is typically exposed to on a daily basis (Wheeler-Hegland et al. 2008). In THS, applied resistance on the pharyngeal wall corresponds to the restricted tongue movements during pharyngeal swallowing (Fujiu and Logemann 1996; Fujiu-Kurachi et al. 2014).
In an original THS study (Fujiu and Logemann 1996), participants were asked to maximally but comfortably protrude their tongue, holding it between the central incisors. In this instruction, “maximally but comfortably” could be interpreted subjectively, thus causing variations in tongue-hold lengths among patients, or within the same patient at different attempts. Therefore, it appears that a more objective criterion is needed for THS. Given that each person has a different tongue length (Fujiu-Kurachi et al. 2014), uniform protrusion of the tongue during THS, regardless of individual tongue length, would cause different effects, contrary to the expectations of many clinicians. It is hypothesized that the greater the tongue protrusion in proportion to individual tongue length, the greater the effort required for further compensation of restricted tongue movement. This increased effort can be measured by suprahyoid muscle surface electromyography (sEMG).
Fujiu-Kurachi et al. (2014) examined the changes in intraoral pressure during THS relative to different degrees of tongue protrusion—dry swallow with no tongue protrusion and THS with 1- and 2-cm tongue protrusion—in 18 young healthy adults. The participants exhibited interesting results. Two types of changes were identified in the maximal magnitude of tongue pressure for posterior intraoral pressure during THS; while eight subjects exhibited an increase in maximal magnitude, along with an increase in the extent of tongue protrusion (increase group), nine exhibited a decrease in maximal magnitude with the increase in extent of protrusion (decrease group). It was found that all eight subjects of the increase group had maximal tongue lengths 32 mm, whereas eight of the nine subjects of the decrease group exhibited maximal tongue lengths 32 mm. The authors suggested the possibility that the tongue of an individual with a greater range of protrusion has sufficient functional reserve for the required tongue movement, even with the tongue-holding maneuver, and is capable of compensating for the constrained movement of the anterior tongue. These results imply that the THS maneuver might require differential application. Therefore, the purpose of this study was to examine the changes in suprahyoid muscle activation during THS relative to different degrees of tongue protrusion in healthy adults.