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

Objective: 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. Method: 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. Results: 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 p s < .05). IM amplitude increased significantly at 80%–100% maximum inspiratory pressure (MIP), exceeding both the swallowing task and all EMT tasks (all p s < .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 p s < .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). Conclusions: 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.