Effect of Different Resistance Respiratory Muscle Training on Swallowing Muscle Activity in Patients With Poststroke...

This study aimed to investigate the activation characteristics of submental muscle (SM) and infrahyoid muscle (IM) in response to expiratory and inspiratory muscle training (EMT/IMT) at varying resistance loads in patients with poststroke dysphagia.

Twenty participants with poststroke dysphagia underwent surface electromyography during 5-ml water swallowing and graded EMT/IMT tasks. Key parameters including amplitude, duration, and root mean square (RMS) were analyzed. Statistical analysis was performed using repeated-measures analysis of variance or the Friedman test, with post hoc Bonferroni correction for multiple comparisons.

The peak amplitude of SM at 75% and 100% maximum expiratory pressure (MEP) was significantly higher than at lower MEP intensities (e.g., vs. 25% MEP, p = .002 and p < .001; vs. 50% MEP, p = .012 and p = .003) and all IMT intensities (all ps < .05). IM amplitude increased significantly at 80%-100% maximum inspiratory pressure (MIP), exceeding both the swallowing task and all EMT tasks (all ps < .05). Except for the affected-side IM during the 80% and 100% MIP tasks, the activity duration of both SM and IM was significantly longer during the 100% MEP task compared to other MEP intensities and all IMT tasks (all ps < .05). RMS values for both muscle groups were elevated at higher respiratory muscle training (RMT) levels. No consistent side-to-side differences were found in most parameters. Borg Dyspnea Scale scores increased progressively with training intensity, with significant differences between high-intensity tasks (e.g., 100% MEP vs. 25% MEP, p < .001; 100% MEP vs. 50% MEP, p = .002; 100% MIP vs. 30% MIP, p < .001).

EMT preferentially activates the SM group in a load-dependent manner, while IMT selectively recruits IM. These findings support the use of targeted, intensity-specific RMT for enhancing swallowing-related muscle activation in rehabilitation.