Six Weeks Inspiratory Muscle Strength Training Lowers Blood Pressure but Does Not Affect Baroreflex Sensitivity or Cardiac Output in Active Young Adults

We showed previously that inspiratory muscle strength training (IMST) lowers resting blood pressure in healthy, college‐aged adults (Vranish and Bailey 2015) and in adults with obstructive sleep apnea (Vranish and Bailey 2016). However, the mechanism underlying IMST‐related declines in blood pressure is unclear. Here, we explore the potential for IMST to modulate baroreflex sensitivity (BRS), cardiac output and /or heart rate in healthy young (19.9±0.3 years) adults (13 men, 12 women). Subjects were randomly assigned to IMST (n=12; 75% maximal inspiratory pressure) or sham training (n=13; 15% maximal inspiratory pressure) groups and underwent 6 weeks of training (30 breaths/day, 5 days/week). Pre‐ and post‐training measures included blood pressure, cardiac output, heart rate, BRS, and maximal inspiratory pressure. Additionally, all subjects completed the Cohen‐Hoberman inventory of physical symptoms survey and the Epworth Sleepiness Scale. Subjects in the IMST group exhibited significant declines in systolic (112.51±2.99 mmHg vs 108.25±3.72 mmHg, p=0.022) and diastolic blood pressures (67.73±2.45 mmHg vs 63.83±2.83 mmHg, p=0.018) whereas resting blood pressures in sham trained subjects were unchanged. IMST trained subjects reported significantly fewer physical symptoms pre vs post training (p=0.025) relative to sham trained individuals (p=0.135). There was no effect on cardiac output (p=0.722), heart rate (p=0.795), or BRS (p=0.776) pre vs post training for either group however, muscle sympathetic nerve activity (MSNA) recorded in four subjects highlights reduced sympathetic nerve traffic in IMST (25.0±6.0 vs 18.5±2.5 bursts/min) relative to sham‐trained (23.6±10.5 vs 23.0±10.0 bursts/min) subjects. Changes in central and /or other reflex modulation of MSNA may underpin IMST related reductions in mean arterial pressure in active young adults.