The Effects of Expiratory Muscle Strength Training on Voice and Associated Factors in Medical Professionals With Voice Disorders

Objectives: This research used expiratory muscle strength training to explore the factors relevant to medical professionals with voice disorders. The maximal expiratory pressure (MEP) improved, which is measured by the maximal contracting force of expiratory muscles. The expiratory muscle strength increased, which can affect the positive pressure of pulmonary volume, thereby influencing subglottal pressure for speech to change the voice performance and vocal-fold vibration. Methods: Twenty-nine participants with voice disorders who are working in a hospital and who are using their voice for more than 4 hours per day were recruited. The participants were randomly assigned to either the study group (STU) or the control group (CON). All participants underwent aerodynamics analysis, pulmonary function, MEP, and completed a vocal symptoms questionnaire before and after STU was provided. The interventions in the STU were conducted 3 days per week and involved performing 25 expiratory exercises (five cycles, each comprising five breaths) for 5 weeks. The CON did not receive any intervention. Results: The voiceless /S/ expiratory time, symptom questionnaire scores, and MEP were greater in the STU than in the CON (P <0.05). However, no statistically significant difference in the results of the pulmonary function was observed between the groups. The STU exhibited a greater percentage change in maximal voiced /Z/ phonation and voiceless /S/ expiratory compared with the CON (P <0.05). Conclusions: The participants' voiceless /S/ expiratory time, symptom questionnaire scores, and MEP significantly improved after the intervention. Future studies can increase the number of participants, increase the number of study groups, and examine the effectiveness of long-term treatment.