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

Objective: Evaluate the short-term physiologic and one-year functional impact of a 12-week inspiratory and expiratory respiratory strength training (RST) program in individuals with amyotrophic lateral sclerosis (ALS).

Methods: A double-blind, 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 pre-test 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: RST 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 cmH₂0 following active-RST (95% CI: +7.6, +33.9) and decreased by 1.0 cmH₂0 (95% CI: -9.1, +7.2) following sham-RST. Mean MIP increased by 8.9 cmH₂0 (95% CI: +1.5, +16.3) and 4.8 cmH₂0 (95% CI: -0.6, +10.2) for the active and sham groups respectively. Secondary Outcomes: RST led to significant increases in cough peak inspiratory flow (p=0.02), however, did not impact cough expiratory flow (p = 0.06) or FVC (p=0.60). Twelve-Month Outcomes: A significant difference in ALSFRS-R Bulbar subscale slope was observed across treatment groups, with a more than two-fold faster rate of bulbar decline in the sham versus 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).

Conclusions: 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.