Effects of Inspiratory Muscle Training on Respiratory Muscle Strength, Respiratory Function and Functional Capacity in Adolescents with Idiopathic Scoliosis : A randomized, Controlled Trial

Background: Adolescent Idiopathic Scoliosis (AIS) may impair respiratory dynamics and affect the performance of inspiratory and expiratory muscles. The benefit of inspiratory muscle training (IMT) is not well investigated in AIS. We aimed to investigate the effects of IMT on respiratory muscle strength, respiratory function and functional capacity in adolescents with mild to moderate AIS.

Methods: Thirty-six adolescents were randomized into control or IMT groups. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and peak expiratory flow (PEF) were measured by spirometry; respiratory muscle strength by maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP); and functional capacity by 6-min walk test (6MWT) before and after the 8-week-long home-based exercise program. Both groups received conventional exercise program including diaphragmatic breathing exercises, resistive local expansion exercise on the collapsed areas in concave sides of scoliosis, spinal stabilization, strengthening of interscapular muscles and stretching exercises. IMT group also trained with Threshold IMT device for 15 minutes, twice a day for 8 weeks at the intensity of 30% of initial MIP value in addition to conventional exercise program.

Results: FEV1, PEF, MIP, MEP and 6MWT distance significantly improved in both groups. IMT group also showed significant improvement in FVC. The increases in FVC, MIP, MEP and 6MWT distance of IMT group were significantly higher compared to control group.

Conclusion: IMT is found to be beneficial for patients with AIS for achieving further improvements in respiratory function, respiratory muscle strength and functional capacity compared to conventional exercise program alone.