The Effects of Respiratory Muscle Training on Phonatory Measures in Individuals with Parkinson's Disease: Effects of Respiratory Muscle Training

Introduction: In individuals with Parkinson's disease (PD), respiratory muscle weakness and rigidity, bradykinesia of abdominal muscles and stiffness of the chest wall, affect the respiratory component of voice intensity due to reduced pulmonary capacity and airflow needed to vibrate the vocal folds. It may be possible to improve voice production by strengthening respiratory muscles. The purpose of this study was to evaluate the effects of inspiratory and expiratory muscle training on voice production outcomes in individuals with PD. Method: Thirty-one participants with PD were randomly allocated to three study groups (control group n = 10, inspiratory training group, n = 11, and expiratory training group, n = 11). The inspiratory and expiratory group performed a home-based inspiratory and expiratory muscle training program, respectively (five sets of five repetitions). Both groups trained six times a week for 2 months using a progressively increased resistance. The control group performed expiratory muscle training using the same protocol and a fixed resistance. Phonatory measures, maximum inspiratory/expiratory pressure, and spirometric indexes were assessed before and at 2 months after training. Results: Differences in peak subglottic pressure were moderate (d = 0.59) between expiratory and inspiratory groups, large between inspiratory and control groups (d = 1.32), and large between expiratory and control groups (d = 1.96). Differences in maximum phonation time were large (d = 1.26) between inspiratory and control groups, moderate (negative) between expiratory and inspiratory groups (d = –0.60), and moderate between expiratory and control groups (d = 0.72). Differences in peak sound pressure level were large (d = 1.27) between inspiratory and control groups, trivial between expiratory and inspiratory groups (d = –0.18), and large between expiratory and control groups (d = 1.10). Conclusions: Inspiratory muscle training is effective in improving maximum phonation time, and expiratory muscle training is more effective for improving peak subglottic pressure, and peak sound pressure level in individuals with PD.