Effects of respiratory muscle training on respiratory muscle strength and heart rate variability in myotonic dystrophy patients type 1

Abstract

Introduction: Myotonic dystrophy (MD) is a multisystemic neuromuscular disease responsible for causing progressive respiratory muscle weakness. Respiratory muscle training (MRT) has been shown to be effective in several diseases; however, its effects on respiratory and cardiac functions in MD are still inconsistent.

Objective: Assess the effects of MRT on respiratory muscle strength and heart rate variability in patients with type 1 myotonic dystrophy. Methods: The sample was composed of 6 individuals of both sexes. The following was assessed: respiratory muscle strength, before and after training (sessions 1-4) and heart rate variability before and after sessions 2 and 3. The group submitted to MRT used the Threshold IMT device, adapted for inspiratory and expiratory training, three times a week, once at an outpatient facility and twice at home. Results were expressed as median and interquartile ranges for pulmonary function variables, and the Friedman and Wilcoxon tests were applied to compare heart rate variability.

Results: respiratory muscle strength significantly improved expiratory and inspiratory muscles (33% and 20%, respectively), considering training sessions 1-4. With respect to variability, there was a 102% increase in sympathetic activity, reflected by low frequency and 194% increase in vagal tonus, represented by high frequency.

Conclusions: Preliminary study results demonstrate that a partial home-based respiratory muscle-training program is feasible, in addition to improving strength and heart rate variability in patients with MD.