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 (n = 17, each group). The training was conducted for similar to 35 min, thrice/week over 12 weeks. The maximal inspiratory (IPmax) and expiratory (EPmax) pressure (indicating the strength of the inspiratory and expiratory muscles, respectively), pulmonary functions [forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC index], and asthma control test (ACT) were assessed before and after the intervention. Results The In/Ex-SC yielded larger increases in IPmax and EPmax than either the Placebo training (P=.031 and P=.009 respectively) or the In-MT (P=.029 and P=.032 respectively). Further, In/Ex-SC produced favorable improvement in FEV1, FVC, and FEV1/FVC compared to the Placebo training (P=.001, P=.004, and P=.0005 respectively) or In-MT (P=.038, P=.037, and P=.025 respectively) training. Furthermore, In/Ex-SC led to better control of asthma symptoms than the Placebo (P<.001) or In-MT (P=.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.