Objectives: Swallowing is a complex sensorimotor event that contains both voluntary and involuntary movements of the orofacial, pharyngeal, laryngeal and esophageal regions and requires coordination of those muscle functioning. A loss of the coordination is associated with dysphagia leading to coughing, pulmonary aspiration and crucial pneumonia. A variety of food consistencies and body and/or head positions are frequently presented for the evaluation and treatment of dysphagia. In this study, the effects of food consistency and body posture on the entire swallowing function were investigated quantitatively. Methods: Thirteen healthy volunteers without complaint of dysphagia or other oropharyngeal ploblems were included in this study. The subject was required to swallow test foods (5 ml) with three different hardness and liquid by the cue, which was so called command swallow. They were also tested in two different postures which were upright and body reclinced at 30 degrees. The videofluorography as well as the tongue pressure and electromyographic activity of suprahyoid muscle were recorded. Results: Swallowing-related movements varied among the foods and postures. Tongue pressure was increased during hard food swallowing as compared with soft food or liquid.

Oral transit time was increased while clearance time was decreased during hard food swallowing as compared with soft food or liquid. When compared between the postures, tongue pressure and bolus flow time except oral transit time tend to be larger in the body reclined than upright. Contrary to this, patterns of suprahyoid muscle activity hardly changed regardless of difference in the posture. Conclusion: The results suggest that food consistency and subject's posture may affect the swallowing function in terms of swallow-related tongue activity and the bolus flow time. Furthermore, simultaneous recordings of videofluorography, electromyography and tongue pressure can be available to evaluate the temporal relationship between biomechanical function and bolus flow during swallowing movements.