Training respiratory muscles, boosting cardiac vagal control: A systematic review and meta-analysis of preclinical and clinical studies.

Abstract

Inspiratory muscle training (IMT) is a respiratory based intervention capable of increasing maximal inspiratory pressure (MIP) and modulating cardiovascular autonomic control. This systematic review and meta-analysis aimed to synthesize and quantitatively evaluate the effects of IMT on cardiorespiratory interactions and autonomic outcomes. Clinical trials assessing MIP and autonomic markers, including heart rate variability (HRV), spontaneous baroreflex sensitivity (BRS), and muscle sympathetic nerve activity (MSNA), were included. Searches were conducted in PubMed, Scopus, and Europe PMC up to June 2025. Risk of bias was evaluated using the Risk of Bias 2 tool, and random effects meta-analyses were performed. Twelve clinical studies involving 274 participants were included in the quantitative synthesis. IMT protocols varied in duration and intensity. IMT significantly increased MIP, corresponding to an approximate 41% improvement compared with 9% in control groups. Subgroup analyses demonstrated consistent effects across training durations and intensities. Regarding autonomic outcomes, IMT increased the high frequency normalized component of HRV, indicating enhanced vagal mediated cardiac modulation, with no observed heterogeneity. In addition, two studies demonstrated reductions in MSNA following IMT, whereas no significant effects were observed for BRS. Approximately 62.5% of studies were classified as low risk of bias, and no high-risk studies were identified. IMT improves inspiratory muscle strength and enhances cardiac vagal modulation, supporting its role as a non-pharmacological strategy to modulate cardiovascular autonomic control. The review was registered in PROSPERO CRD420251021003.