Efficacy and safety of respiratory strength and endurance training in patients with myotonic dystrophy type 1 (DM1): a randomized controlled trial.

Background: Myotonic dystrophy type 1 (DM1) is a multisystem disorder characterized by progressive muscle weakness, including the respiratory muscles, which often leads to ventilatory insufficiency. Despite its clinical relevance, high-quality controlled data on the effects of respiratory muscle training in DM1 are limited.

Objective: To evaluate the safety and effectiveness of long-term, home-based inspiratory muscle training (IMT) using a commercially available inspiratory training device in genetically confirmed DM1 patients.

Methods: This was a single-center, randomized controlled trial involving three parallel groups: inspiratory strength training, inspiratory endurance training, and a control group without training. Patients were followed over 9 months. The primary outcome was the change in maximal inspiratory pressure (MIP) after nine months. Secondary outcomes included forced vital capacity, maximal expiratory pressure, capillary blood gases, a 6-min walk test, and validated patient-reported outcomes. Adherence and safety were monitored.

Results: Twenty-six participants completed the study. The intervention was safe, with no serious adverse events. Significant improvements in primary outcome MIP were observed in both intervention groups compared to control (p < 0.05), with the strength group showing the greatest benefit. Secondary outcomes improved significantly in the endurance group. Adherence to the training exceeded 80% across all groups. Baseline differences in MIP, FVC, and FEV1 were observed and considered in the analysis.

Conclusion: Regular IMT is a feasible, safe, and effective intervention for improving respiratory function in patients with DM1. Regular RMT can enhance respiratory muscle strength and endurance and should be incorporated into the multidisciplinary care of DM1 patients showing initial signs of restrictive ventilatory insufficiency.