JMIR Res Protoc. 2025 Jul 28;14:e68582. doi: 10.2196/68582.ABSTRACTBACKGROUND: Bronchodilators (BDs) have been used therapeutically to improve exercise capacity in patients with other chronic respiratory diseases. However, the effect of BDs on the exercise capacity of individuals with non-cystic fibrosis bronchiectasis (NCFB) is poorly understood.OBJECTIVE: The aim of this study was to evaluate the effects of BDs on exercise capacity and thoracoabdominal kinematics in patients with NCFB.METHODS: This crossover randomized controlled trial will involve 45 outpatients with NCFB aged 18 to 59 years. They will be evaluated in 3 visits. On day 1, the maximal exercise capacity (cardiopulmonary exercise test; peak work rate [Wpeak]) will be assessed. On day 2, individuals will be randomized to receive either BD (ipratropium bromide 160 µg and fenoterol hydrobromide 400 µg) or a placebo and then undergo simultaneous endurance exercise capacity (constant work-rate exercise test) and thoracoabdominal kinematics (optoelectronic plethysmography) assessments. After at least 1-week washout (day 3), the individuals will repeat the same assessments as on day 2 in the reverse order. The time to the limit of tolerance will be obtained in both groups (BD and placebo groups) as the primary outcome. Thoracoabdominal kinematics will be assessed at 3 time points: at rest, during unloaded exercise, and at 75% Wpeak. The total chest wall and compartmental volumes as well as thoracoabdominal asynchrony will be assessed. The assessors and patients will be blinded to the interventions (BDs or placebo). Data will be compared using 1-sided t tests or Wilcoxon tests and repeated-measures analysis of variance or Friedman tests. Categorical data will be analyzed using the chi-square test or Fisher test. The associations among variables will be analyzed using Pearson or Spearman correlation. The significance level will be set at 5% (P