Sole-ground contact and sitting leg position influence suprahyoid and sternocleidomastoid muscle activity during swallowing of liquids.

Clinically, the stable sole-ground contact in the diet is considered as important for achieving safe swallows in the dysphagic patients. However, the effects of varied sole-ground contacts on swallow-related muscles activities remain unclear. The aim of this study was to investigate the effects of sole-ground contacts on the muscle activities during swallow for various materials; 26 healthy adult subjects participated in this study. Three different sole-ground contact conditions were investigated; sole-ground contact with knees bent to 90° (KB 90°), sole-ground contact with knees bent to 135° (KB 135°), and sole-ground off the floor (Off). Participants swallowed four bolus materials (saliva, 5-ml water, 10-ml water, and 5-ml yogurt) in each sole-ground contact condition. The muscular activities of the suprahyoid (SH) muscle and the sternocleidomastoid muscle during swallowing were detected and recorded using surface electromyography. The sole-ground contact pressure was evaluated using the data acquisition system. Duration of SH during 10-ml water swallow for Off was significantly longer than that for KB 90°. Duration of SH during 5-ml yogurt swallow for Off was significantly longer than that for KB 90°. Integration of SH during 10-ml water swallow for Off was significantly greater than that for KB 135°. Integration of SH during 5-ml yogurt swallow for Off was significantly greater than that for KB 90°. No significant differences were found in peak of SH. Sole-ground contact conditions had significant effect on swallow-related muscles activities. The stable sitting positions might be more advantageous for performing effective swallows compared with less stable sitting positions.