The Rationale of Applying Inspiratory/expiratory Muscle Training Within the Same Respiratory Cycle in Children with Bronchial Asthma: a Placebo-controlled Randomized Clinical Investigation

Objective: Even though positive implications of inspiratory muscle training (In-MT) have been established in children and adolescents with bronchial asthma (C/AwBA), the role of combined inspiratory and expiratory muscle training (Ex-MT) within the same respiratory cycle (In/Ex-SC) is still unknown. This study was, therefore, set out to explore the effect of In/Ex-SC on respiratory muscle strength, pulmonary functions, and control of asthma symptoms in C/AwBA.

Methods: This was a placebo-controlled randomized clinical investigation that included 51 C/AwBA (12-18 years). Participants were assigned randomly into three groups: Placebo, In-MT only, or combined In/Ex-SC training ( = 17, each group). The training was conducted for ∼35 min, thrice/week over 12 weeks. The maximal inspiratory (IP) and expiratory (EP) pressure (indicating the strength of the inspiratory and expiratory muscles, respectively), pulmonary functions [forced expiratory volume in one second (FEV), forced vital capacity (FVC), and FEV/FVC index], and asthma control test (ACT) were assessed before and after the intervention.

Results: The In/Ex-SC yielded larger increases in IP and EP than either the Placebo training (=.031 and =.009 respectively) or the In-MT (=.029 and =.032 respectively). Further, In/Ex-SC produced favorable improvement in FEV, FVC, and FEV/FVC compared to the Placebo training (=.001, =.004, and =.0005 respectively) or In-MT (=.038, =.037, and =.025 respectively) training. Furthermore, In/Ex-SC led to better control of asthma symptoms than the Placebo (<.001) or In-MT (=.002) training.

Conclusion: This study provides evidence that combined In/Ex-SC can considerably improve respiratory muscle strength, enhance pulmonary function, and promote control over asthma symptoms in C/AwBA.