Objective: To analyze the effectiveness of Expiratory Muscle Strength Training (EMST) combined with Water Resistance Voice Therapy (WRVT) on vocal aspects of individuals with Parkinson’s disease (PD), comparing the order in which these interventions were performed.
Methods: This study was designed as a randomized, controlled, crossover clinical trial. Twenty-three individuals with PD, preserved cognition, and hypokinetic dysarthria (H&Y stages 2–3) participated. They were allocated into two groups: EMST-first (n=12; 5 women, mean age 70.8 years; 7 men, mean age 72.1 years) and WRVT-first (n=11; 3 women, mean age 69 years; 8 men, mean age 65.5 years). All participants received both EMST and WRVT in randomized order. The EMST-first group began with eight EMST sessions, twice a week, complemented by home practice five days a week using the EMST150 device, followed by WRVT. The WRVT-first group completed eight 45-minute voice therapy sessions, twice weekly, including semi-occluded vocal tract exercises using a glass tube immersed in water, also complemented by home practice, and then proceeded to EMST. Assessments were performed at three time points: M1 (baseline), M2 (post-interventions), and M3 (30-day follow-up). Analyses included vocal intensity, vocal quality through perceptual-auditory and acoustic evaluations, electroglottographic assessment, aerodynamic measures, vocal symptom self-assessment, and voice-related quality of life. Data were analyzed using repeated-measures ANOVA (p≤0.05).
Results: After the interventions (M2), both groups showed increased vocal intensity during sustained vowel (p<0.002), number counting (p<0.001), and spontaneous speech (p = 0.005). Increases in Cepstral Peak Prominence Smoothed (CPPS) during number counting (p<0.001) were also observed (M2), along with reduced frequency of vocal symptoms (p<0.001) and improved voice-related quality of life (p=0.001). At follow-up (M3), gains were maintained only in self-assessment measures (social-emotional score – voice-related quality of life, p=0.020). No significant changes were found in perceptual-auditory voice quality analysis, and electroglottographic, multiparametric acoustic, or aerodynamic measures in either group.
Conclusion: The combination of Expiratory Muscle Strength Training and Water Resistance Voice Therapy was effective in individuals with PD, promoting increased vocal intensity, higher CPPS values, fewer vocal symptoms, and improved voice-related quality of life, regardless of the order in which the interventions were provided.