Tongue pressure is generated not on

Tongue pressure is generated not only by the intrinsic tongue musclesincluding the superior and inferior longitudinal, transverse and vertical muscles 1, butalso by the extrinsic tongue muscles including the genioglossus, styloglossus and hyoglossus, and even the suprahyoid (S-hyo) muscles such as mylohyoid and digastric muscles 4,5. A number of previous studies reported lower tongue pressure in dysphagic patients suffering from neurodegenerative Parkinson’s disease 6,7,amyotrophic lateral sclerosis disease 8 and stroke 9-12. In Japan, substantial aging ofsociety has occurred over the last several decades. Oral health conditions, including the tongue motor function required to produce tongue pressure in elderly community dwellers exhibits wide variation, from normal function to malfunction 13. Tonguepressure generation generally declines with aging, which affects mastication, bolus formation and swallowing and may lead to insufficient food intake to meet the amount of nutrition required 14. Tongue strength training has been reported to improve swallowing function in stroke patients 12,15 and older people 16. These reports suggestthat improvement of swallowing function following tongue pressure strength training can be produced by strengthening both the tongue and hyoid muscles 2Correlation between tongue pressure and electromyographic (EMG) activity of the S-hyo muscle was confirmed during lingual exercises 4,17. Fukuoka et al 17reported that EMG activity of the S-hyo muscle induced by isometric tongue lift movement (TLM) was increased during therapeutic exercises, including head lift exercise, the Mendelsohn maneuver, and tongue protrusion. The authors concluded that isometric lingual exercise provides a useful method for strengthening the S-hyo muscles. However, no previous study has clarified how hyoid muscle function is temporally affected by continuous isometric TLM, or whether TLM contributes to improvement of swallowing function in dysphagic patients and elderly community dwellers.