Effect of expiratory muscle strength training (EMST) on vowel articulation in individuals with Parkinson's disease

Abstract

The present study aimed to investigate the effect of EMST on improving vowel articulation in individuals with Parkinson’s Disease (PD). Data from 16 Cantonese-speaking PD participants who completed four-week intensive training using a calibrated, one-way pressure threshold trainer were randomly selected from a previous study conducted by Tong (2018). Acoustic signals associated with prolongation of the corner vowels (/i/, /a/, /u/) before and after training were examined. By comparing the acoustical parameters: (1) F1 and F2, (2) Triangular Vowel Space Area (tVSA), (3) Vowel Articulation Index (VAI), and (4) Formant Centralization Ration (FCR) before and after EMST, the impact of EMST was revealed. Pre- and post-treatment comparisons revealed significant increase in F2 of /i/ females and F1 and F2 of /a/, as well as F1 of /i/ for males. In addition, tVSA values significantly increased in both genders, indicating an enlarged articulatory region for vowel production by PD participants after EMST. Yet, no statistical significance was found for VAI and FCR. The inconsistent findings may suggest a discoordination between respiratory and articulatory subsystems with a less direct biomechanical and neural control interconnection.