Effect of expiratory muscle strength training on voice and speech: An exploratory study in persons with Parkinson's disease or multiple sclerosis.

Purpose: This study explored how respiration, voice, and speech were affected following expiratory muscle strength training (EMST) and maintenance training in persons with Parkinson's disease (PD) or multiple sclerosis (MS).
Method: Nine participants with PD and six with MS participated in a randomised study, where the effects of EMST, sham, and maintenance treatment were investigated. Outcome measures included maximum expiratory pressure (MEP); maximum phonation time (MPT); intelligibility; verbal diadochokinesis (DDK); speech rate; a self-report form on voice, speech, and communication; and open questions about how the participants experienced the intervention. Group comparisons were performed within and between groups.
Result: The PD and the MS groups both improved significantly in MEP, and this improvement remained after 3 months of maintenance EMST. An improvement was also seen in DDK. Post-EMST, 33% of the PD group and 80% of the MS group reported a positive effect on communication.
Conclusion: The results of this study support previous evidence that EMST has positive effects on expiratory pressure in persons with PD or MS, but its effect on voice and speech remains unclear. Since subjective reports of the intervention and effects on communication were predominantly positive, further research is needed on larger groups to explore appropriate outcome measures.