Time‐Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above‐Normal Blood Pressure

Background High‐resistance inspiratory muscle strength training (IMST) is a novel, time‐efficient physical training modality. Methods and Results We performed a double‐blind, randomized, sham‐controlled trial to investigate whether 6 weeks of IMST (30 breaths/day, 6 days/week) improves blood pressure, endothelial function, and arterial stiffness in midlife/older adults (aged 50–79 years) with systolic blood pressure ≥120 mm Hg, while also investigating potential mechanisms and long‐lasting effects. Thirty‐six participants completed high‐resistance IMST (75% maximal inspiratory pressure, n=18) or low‐resistance sham training (15% maximal inspiratory pressure, n=18). IMST was safe, well tolerated, and had excellent adherence (≈95% of training sessions completed). Casual systolic blood pressure decreased from 135±2 mm Hg to 126±3 mm Hg ( P <0.01) with IMST, which was ≈75% sustained 6 weeks after IMST ( P <0.01), whereas IMST modestly decreased casual diastolic blood pressure (79±2 mm Hg to 77±2 mm Hg, P =0.03); blood pressure was unaffected by sham training (all P >0.05). Twenty‐four hour systolic blood pressure was lower after IMST versus sham training ( P =0.01). Brachial artery flow‐mediated dilation improved ≈45% with IMST ( P <0.01) but was unchanged with sham training ( P =0.73). Human umbilical vein endothelial cells cultured with subject serum sampled after versus before IMST exhibited increased NO bioavailability, greater endothelial NO synthase activation, and lower reactive oxygen species bioactivity ( P <0.05). IMST decreased C‐reactive protein ( P =0.05) and altered select circulating metabolites (targeted plasma metabolomics) associated with cardiovascular function. Neither IMST nor sham training influenced arterial stiffness ( P >0.05). Conclusions High‐resistance IMST is a safe, highly adherable lifestyle intervention for improving blood pressure and endothelial function in midlife/older adults with above‐normal initial systolic blood pressure. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03266510.