Effect of Functional Inspiratory Muscle Training Versus Inspiratory Muscle Training on Trunk Control and Respiratory Functions in Individuals With Chronic Stroke: A Randomized, Controlled, Double-Blind Study

Objective: To compare the effects of functional inspiratory muscle training (FIMT) with inspiratory muscle training (IMT) in individuals with chronic stroke. Design: Prospective, randomized controlled, double-blinded trial. Setting: Department of Physiotherapy and Rehabilitation. Participants: Forty-two individuals (N=42) with chronic stroke (mean age 62.9y, 36.4% women in the FIMT group; mean age 60.3±8.3y, 40.9% women in the IMT group) completed the study. Interventions: Both groups received neurodevelopmental therapy (NDT) 3 times per week for 8 weeks. The FIMT group performed inspiratory muscle training simultaneously with NDT-based functional exercises (eg, bridging, kneeling, weight transfer), whereas the IMT group performed inspiratory training separately, combined with NDT in the same session. All participants also completed a home-based IMT program twice weekly. Main Outcome Measures: The primary outcomes were the Trunk Impairment Scale (TIS) and maximal inspiratory pressures (MIP). Secondary outcomes included Trunk Control Test, maximal expiratory pressures (MEP), respiratory endurance (incremental threshold loading [ITL] test), spirometry values (Forced Expiratory Volume in the First Second, Forced Vital Capacity), balance (Berg Balance Scale), gait (timed Up and Go, 10-Meter Walk Test), core muscle activity (PRONE test), functional capacity (6-Minute Walk Test [6MWT]), and independence (Barthel Index [BI]). Results: Both groups showed significant improvement in most outcome measures after training. However, the FIMT group demonstrated notably greater gains in trunk control (TIS and Trunk Control Test), respiratory muscle strength and endurance (MIP, maximal expiratory pressures, and incremental threshold loading), balance, walking speed, and transversus abdominis activity (P<.05). The mean between-group difference in TIS change was 2.62 points (95% confidence interval [CI], 1.67-3.57), with the lower bound of the CI exceeding the smallest worthwhile effect (0.31). FIMT also yielded superior improvements in MIP (7.48 cm H₂O; 95% CI, 2.43-12.52). No significant differences were observed between groups in 6-Minute Walk Test distance, spirometry results, or Barthel Index scores. Conclusions: FIMT produced greater improvements than IMT in trunk control, respiratory muscle function, balance, and gait speed in individuals with chronic stroke, suggesting it as a promising rehabilitation approach.