Expiratory muscle strength training in individuals with multiple sclerosis and healthy controls

Multiple sclerosis (MS), a demyelinating disease of the central nervous system (CNS), may result in weakness of the respiratory muscles. Weakness of the expiratory muscles may impair effectiveness of cough and the ability to speak. No study has examined expiratory strength training in individuals with mild to moderate disability because of their MS. Purpose. The purpose of this project was to examine the effect of pressure-threshold strength training of the expiratory muscles of respiration on cough effectiveness and speech loudness and prolongation. Subjects. Seventeen individuals with MS and 14 healthy controls used a pressure-threshold device (Threshold PEP) to strength train their expiratory muscles. Procedures . Subjects trained 5 days per week for 8 weeks followed by 4 weeks of no training. Results. Maximal expiratory pressure (MEP), the measurement of expiratory muscle strength, was less than normal for the persons with MS (PwMS) and was significantly less than the healthy controls (H) prior to and after training. PwMS and H subjects significantly improved MEP (p < 0.0001) following training. Significant difference was found in the rise time of maximal voluntary cough in individuals with MS and the healthy subjects. Cough volume acceleration (CVA) was less in PwMS compared to the H each time it was evaluated. Significant differences between the PwMS and the H were found in speech acoustic components, i.e., vowel prolongation and words per minute, and aerodynamic component, i.e., phonation at normal and loud sound pressure level. Discussion. Minimal changes found in cough effectiveness may have occurred secondary to lack of training specificity. Additionally, the components of cough measured may not have been adequate to assess the affect of expiratory muscle strength training on maximal voluntary cough. Subjects stated they could talk louder and though no PwMS reported problems with shortness of breath prior to training, PwMS reported easier breathing after training. Conclusions. Pressure threshold strength training of the expiratory muscles benefits PwMS by increasing MEP which improves vocalization. However, based on the measurements of effectiveness of cough used in the current study, pressure threshold strength training does not improve maximal voluntary cough.