(217) Effects of Expiratory Muscle Strength Training on Voice and Speech in Parkinson's Disease

Introduction: Individuals with Parkinson’s disease (PD) commonly experience hypokinetic dysphonia associated with impaired respiratory support. This systematic review evaluates the effects of expiratory muscle strength training (EMST) on expiratory strength, voice, and speech outcomes in individuals with PD.

Methods: A PRISMA-guided systematic review of studies evaluating EMST in adults with Parkinson’s disease was conducted using PubMed, Embase, and Web of Science (2000-2025). A total of 222 records were screened, 18 full-text articles were reviewed, and 6 studies met the inclusion criteria. Randomized and non-randomized studies were included, with extracted variables encompassing EMST parameters, expiratory strength (maximum expiratory pressure [MEP]), voice and speech outcomes, and patient-reported measures; results were synthesized narratively.

Results: Eighty-eight individuals with PD met the inclusion criteria. Participants were older adults (mean age 66.4-70.1 years) with Hoehn and Yahr stages I-III disease. EMST was delivered as a primary intervention in all studies, most commonly using the EMST150 device, for 4-8 weeks, and resistance levels at 50-75% of baseline MEP. All studies demonstrated improvements in MEP following EMST. Four studies reported voice or speech outcomes, with modest improvements in sustained vowel phonation measures, including sound pressure level and maximum phonation time, and improvements in patient-reported voice measures in select cohorts. In contrast, sentence-level and conversational speech outcomes, including speech intelligibility and utterance length, demonstrated variable or inconsistent responses.

Conclusions: EMST improves expiratory muscle strength in individuals with PD and is associated with modest gains in sustained phonation; however, these benefits do not consistently extend to conversational speech, suggesting that impaired glottic closure may limit functional communication. Further studies are needed to assess the outcome of EMST following interventions improving glottic closure in PD patients.