Resting Blood Pressure Reductions Following Isometric Leg Exercise Training Are Associated With Improved Flow-mediated Vasodilatation

Abstract

Brachial artery flow-mediated dilatation (BAFMD) is an endothelium-dependant and nitric oxide specific index of endothelial function. The chronic effect of isometric exercise on endothelial function remains equivocal. PURPOSE: To investigate whether isometric bilateral leg extension training can reduce resting blood pressure (RBP) and whether these changes are associated with altered BAFMD. METHOD:14 healthy normotensive males volunteered for an 8 week cross-over training study. Exercise intensity for each participant was calculated as 105.4% of 2 minute mean peak torque. Parameters measured at baseline, 4 weeks and post exercise and control condition were used for analysis. Blood pressure was measured using an automated device. Doppler Ultrasound was used to measure change in BAFMD expressed as relative, absolute and normalised to shear rate. RESULTS: Statistically significant reductions were observed in resting systolic blood pressure (-3.56mmHg; p=0.014) and reductions in mean arterial pressure (-3.26mmHg; p=0.027) between exercise and control conditions when measured from baseline to 4 weeks. No significant reductions were observed in resting diastolic blood pressure (p=0.416) and heart rate between conditions from baseline to 4 weeks (p=0.854). A negative correlation of moderate strength was observed between changes in resting mean arterial pressure and BAFMD from baseline to 4 weeks (r=-0.54; p<0.05). No significant differences were observed in resting blood pressure parameters between exercise and control conditions from 4weeks to post (p<0.05).CONCLUSION: Our results demonstrate greater reductions in RBP are associated with enhanced BAFMD. Nitric oxide mediated endothelial function may be an initial mechanism responsible for the RBP reductions. Artery diameter, blood flow patterns, cardiac output and total peripheral resistance are currently undergoing analysis. This may enhance our understanding of the interaction between the physiological mechanisms responsible for reductions in resting blood pressure. This research could potentially inform future alternative exercise prescription for training studies which ultimately aim to improve cardiovascular health.