Dose-dependent effects of inspiratory muscle training in neuromuscular disorders

The goal of this study was to show whether a correlation exists between the intensity of specific respiratory muscle training and the improvement of s trength and endurance in inspiratory musculature in patients with neuromusc ular disorders (NMD). Sixteen patients with NMD (13 with Duchenne muscular dystrophy and 3 with spinal muscular atrophy) performed inspiratory muscle training (IMT) at home with a special training apparatus for 9 months. Maxi mal inspiratory mouth pressure (PIMAX) and 12s-maximum voluntary ventilatio n (12s-MVV) test served as parameters for inspiratory muscle strength and e ndurance, respectively. In patients whose inspiratory vital capacity (VCin) declined by less than 10% during the year before training began (n = 10), a significant positive correlation was found between the number of successf ully completed strength and endurance exercises and the improvement of PIMA X (P < 0.05) and 12s-MVV (P < 0.05). In patients whose VCin-decline exceede d 10% (n = 6), indicating more progressive respiratory system involvement o f the disease, no significant correlation between the improvement of PIMAX and 12s-MVV and the intensity of training was found. In patients with NMD, the effects of IMT-runs are dose-dependent, provided that the respiratory s ystem involvement of the disease is only slowly progressive. (C) 2000 John Wiley & Sons, Inc.