Respiratory Strength Training in Amyotrophic Lateral Sclerosis: A Double-Blind, Randomized, Multicenter, Sham-Controlled Trial

Abstract

Background and objective: The objective of this study was to evaluate the short-term physiologic effect and one-year functional effect of a 12-week inspiratory and expiratory respiratory strength training (RST) program in individuals with amyotrophic lateral sclerosis (ALS).

Methods: A double-blinded, randomized, sham-controlled trial was conducted in 45 individuals with early-stage ALS. Participants were randomized into 12 weeks of active RST (30% load, n = 23) or sham RST (0% load, n = 22). An intent-to-treat analysis was conducted. Linear regression of pre-post change with group status and pretest scores as predictors was conducted. Primary outcomes included maximum expiratory and inspiratory pressure (MEP, MIP), and secondary outcomes were cough spirometry and forced vital capacity. Exploratory follow-up outcomes included one-year global and bulbar decline (ALS Functional Rating Scale-Revised [ALSFRS-R] total and bulbar subscale slope), oral intake status, and time to noninvasive ventilation (NIV).

Results: TheRST completion rate was 91% with no RST-related adverse events. A 12-week RST program led to increases in MEP (p = 0.004), but not MIP (p = 0.33). On average, MEP increased by 20.8 cm H₂O after active RST (95% CI +7.6 to +33.9) and decreased by 1.0 cm H₂O (95% CI -9.1 to +7.2) after sham RST. Mean MIP increased by 8.9 cm H₂O (95% CI +1.5 to +16.3) and 4.8 cm H₂O (95% CI -0.6 to +10.2) for the active and sham groups, respectively. Regarding secondary outcomes, RST led to significant increases in cough peak inspiratory flow (p = 0.02); however, it did not affect cough expiratory flow (p = 0.06) or FVC (p = 0.60). Regarding 12-month outcomes, a significant difference in the ALSFRS-R bulbar subscale slope was observed across treatment groups, with a more than two-fold faster rate of bulbar decline in the sham vs active RST groups observed (-0.29 vs -0.12 points/month, p = 0.02). Total ALSFRS-R slope, feeding status, and time to NIV did not differ across treatment groups (p > 0.05).

Discussion: RST was well tolerated and led to improvements in some, but not all, short and long-term outcomes. RST represents a proactive rehabilitative intervention that could increase physiologic capacity of specific breathing and airway clearance functions during the early stages of ALS. Further work is needed to determine optimal training intensity, resistance load specifications, and potential long-term functional outcomes.

Classification of evidence: This study provides Class II evidence that a mild-intensity respiratory strength training program improves maximum expiratory pressure, but not maximum inspiratory pressure, in patients with early-stage ALS.