Multiple clinical trials and meta-analyses consistently demonstrate that inspiratory and expiratory muscle training enhances respiratory muscle strength and pulmonary function across various populations.
The provided literature consists of multiple randomized controlled trials, systematic reviews, and meta-analyses showing that inspiratory and expiratory muscle training consistently improves respiratory muscle strength, lung function parameters (such as FEV1 and FVC), and related physiological outcomes in diverse populations, including asthma, stroke, burns, and surgical patients. There are no papers contradicting the claim.