Acute Effects of Inspiratory Muscle Strength Exercise on Vascular Function and Shear Pattern in Young Adults

Purpose: Inspiratory muscle strength training is a time-efficient strategy for lowering blood pressure, but the acute vascular effects and its hemodynamic characteristics remain unclear.This study aimed to determine the acute effects of inspiratory muscle strength exercise (IMSE) on vascular function and shear patterns.Methods: In a single-arm acute trial, 12 young adults (aged 26±2 years) performed a single bout of IMSE (about 8 minutes) consisting of 30 breaths (6 breaths×5 sets) at 60% of maximal inspiratory pressure.Vascular function indices were assessed as endothelial function and arterial stiffness.Measurements of endothelial function via flow-mediated dilation (FMD) in the brachial artery and arterial stiffness by carotid-femoral pulse wave velocity (cfPWV) were taken at baseline, 10 minutes, and 40 minutes post-IMSE.Shear rate (SR) responses were continuously obtained throughout the IMSE session at the brachial artery and were analyzed as mean SR, anterograde SR, and retrograde SR.Results: Compared to baseline, cfPWV significantly decreased (7.95±0.9m/sec to 7.49±0.9m/sec, p=0.033) and FMD increased (4.76%±1.0%to 6.26%±1.1%,p＜ 0.001) at post-10 min.Both cfPWV and FMD returned to baseline levels at post-40 min.During IMSE, mean SR and anterograde SR significantly increased (both, p＜ 0.05), whereas retrograde SR decreased (p=0.032)during inter-set rest periods.In addition, rhythmic fluctuations in SR were observed corresponding to inspiration and expiration phases.Conclusion: These findings suggest that an acute bout of IMSE is associated with improved endothelial function and arterial stiffness.IMSE may elicit distinct hemodynamic responses during exercise, which may be linked to improvements in vascular function.