Effect of body inclination on suprahyoid muscle activity during repetitive voluntary swallowing: A randomized crossover study.

Abstract

This study examined how body inclination affects swallowing dynamics by analyzing suprahyoid muscle activity during repetitive voluntary swallowing with minimal pharyngeal sensory stimulation. Fourteen healthy female volunteers participated. Surface electromyography (EMG) was recorded from suprahyoid muscles during repetitive voluntary swallowing with slow infusion (0.2 mL/min) of 0.3 M NaCl solution. Measurements were taken at four angles: upright (90°), reclined at 60°, reclined at 30°, and supine (0°). Body inclination significantly affected swallowing intervals (SI) and EMG burst duration. The upright position showed significantly shorter SIs compared to 60° reclined and supine positions. The 30° reclined position also demonstrated shorter swallowing intervals than supine. EMG burst duration was significantly shorter in the upright position compared to all reclined positions. No significant differences were observed in EMG amplitude across different angles. This study demonstrates that greater reclining angles (60° or more) make voluntary repetitive swallowing more difficult. Findings suggest that dysphagia rehabilitation should be conducted at positions elevated at least 30° from supine for optimal outcomes.