GOZAL, D., and P. THIRIET. Respiratory muscle training in neuromuscular disease: long-term effects on strength and load perception. Med. Sci. Sports Exerc., Vol. 31, No. 11, pp. 1522–1527, 1999.
Purpose: Deterioration of respiratory muscle function in patients with neuromuscular disorders is primarily responsible for the high morbidity and mortality associated with these diseases.
Methods: The potential benefit of respiratory muscle training (RMT) on preservation of respiratory muscle strength and respiratory load perception (RLP) was examined in 21 children (mean age: 12.2 ± 1.8 yr [SD], 16 male) with Duchenne’s muscular dystrophy or spinal muscular atrophy type III, and in 20 age-, weight-, and sex-matched controls. Subjects were randomly allocated to undergo incremental RMT with resistive inspiratory and expiratory loads for a period of 6 months (trained group, TR) or to perform similar exercises with no load (NT). Maximal static inspiratory (Pimax) and expiratory (Pemax) pressures and RLP (modified Borg visual analog scale 0–10) were assessed on two separate occasions before beginning of the training protocol, monthly throughout RMT duration, and every 3–6 months upon cessation of RMT for 1 yr.
Results: In controls, no significant changes in maximal static pressures or load perception occurred during RMT or thereafter. Training in neuromuscular disorder (NMD) patients was associated with improvements in Pimax (mean Δmax: +19.8 ± 3.8 cmH2O in TR vs +4.2 ± 3.6 cmH2O in NT;P < 0.02) and in Pemax (mean Δmax: +27.1 ± 4.9 cmH2O in TR vs −1.8 ± 3.4 cmH2O in NT;P < 0.004). Similarly, RLP significantly decreased during the RMT period in TR (mean Δ: 1.9 ± 0.3;P < 0.01) but did not change in NT (−0.2 ± 0.2). In addition, with cessation of RMT, static pressures returned to pretraining values in TR within ∼3 months. However, RLP was still improved after 12 months.
Conclusions: We conclude that in children with NMD, although RMT-induced increases in expiratory muscle strength are rapidly reversible, long-lasting improvements in RLP occur and could be associated with decreased respiratory symptoms.