Isometric Exercise Training, Regardless Of Muscle Mass, Reduces Resting Blood Pressure In Normotensive Healthy Males

Abstract

PURPOSE: Isometric exercise training (IET) is an effective adjunct for the management of resting blood pressure (RBP) but responsible mechanisms have not yet fully been identified. Isometric contractions reduce blood flow as a result of vascular compression altering intramuscular metabolism. In response, active muscle could increase the production and circulation of vasoactive molecules (e.g., VEGF) and alter inflammatory biomarkers (e.g., IL-6 and TNF-α), which may lead to adaptations in resistance vessels. We studied the influence of bilateral arm or leg IET on blood pressure and plasma VEGF, IL-6, and TNF-α over the course of 6-weeks. METHODS: The study was approved by the UNC Charlotte IRB. Twenty-eight healthy and recreationally active normotensive males (19-25 years) gave written informed consent and were randomized to one of three conditions; double bicep curl IET (IBC), double leg extension IET (ILE), or control (CON). IET groups completed exercise sessions at 15% maximal voluntary contraction (6 x 2-minute contractions) 3 days per week for 6-weeks with RBP assessed at each visit. For a subsample (n=17), 3 blood samples (pre-, 1 hour post-, 24 hours post-training) were collected at the first and last training visits. The CON group performed all study procedures except IET. RESULTS: Using a repeated-measures ANCOVA (controlling for acclimation RBP and cohort), a significant time by treatment effect was observed from Week 1 to Week 6, F(2, 23) = 4.10, p=.03, η2 = .263. Specifically, IET resulted in a lower systolic RBP, but did not differ by IET group: IBC -4.4 ± 4.0 mmHg; ILE -4.3 ± 7.6 mmHg; CON 2.3 ± 4.0 mmHg. Diastolic RBP did not significantly change for any group. Currently, there are no acute or chronic IET effects on the systemic biomarker levels. CONCLUSIONS: 6-weeks of bilateral arm or leg IET resulted in significant reductions in systolic RBP. Due to the small sample size (n=17), power may have limited the ability to detect significant effects on circulating VEGF, TNF-α and IL-6. Research should continue to examine how IET alters RBP. The research was funded by Faculty Research Grant (JMB & HR) and the Thomas L. Reynolds Graduate Student Research Award (B.D.H.G)