Effect of High vs. Low Intensity Expiratory Muscle Strength Training on Swallowing in People with Degenerative Parkinsonism: A Randomized Controlled Trial

In this study, we investigating the comparative efficacy of training intensity in terms of adherence and patient-reported outcomes. Specifically, we aimed to establish the optimal balance between training intensity and adherence to a modified (low-intensity) expiratory muscle strength training (EMST) protocol in degenerative parkinsonism. No randomized controlled trial has been conducted to evaluated the efficacy of such a modified EMST protocol compared with the conventional protocol to date. Thirty participants were randomly assigned to high- and low-intensity groups and completed a 6-week EMST program. The high-intensity group demonstrated significant improvements in respiratory function, measured as the maximal expiratory pressure (MEP) and peak cough flow, and in swallowing function, assessed via the penetration–aspiration scale and the Normalized Residue Ratio Scale (NRRS) for the vallecular spaces. The low-intensity group showed significant improvements in swallowing function measures only. Correlation analyses revealed that, in the high-intensity group, improvements in the maximal inspiratory pressure were significantly associated with improvements in swallowing function, while improvements in the MEP were significantly correlated with reductions in the NRRS (vallecular) score. Quality of life related to swallowing, measured using the Korean version of the Swallowing Quality of Life questionnaire total score, improved significantly in both groups. Taken together, high-intensity EMST resulted in broader improvements across respiratory and swallowing function, while the groups demonstrated comparable improvements in swallowing-related quality of life. Therefore, although high-intensity EMST may provide more comprehensive benefits, adapting the training intensity based on patient tolerance and adherence may render low-intensity protocols a reasonable alternative for selected patients.