Background: Acute dietary nitrate (NO₃-) supplementation with beetroot juice (BRJ) can lower blood pressure (BP) at rest and during exercise in healthy individuals; however, the effects on endothelial function and BP response to dynamic exercise are not known in prehypertensive individuals. We compared the effects of 15 days BRJ supplementation on hemodynamic responses during progressive dynamic exercise. 

Methods: In a double-blind, randomized, crossover design, 11 healthy, prehypertensive men were supplemented with either BRJ (5.6 mmol, 70 ml BRJ) or a placebo (PL)(70 ml control drink) every day for 15 days. Participants completed two bouts of cycling exercise at each of the two 

workout intensities, corresponding to 30% and 60% of their predetermined VO_2peak values. Flow-mediated dilation (FMD) of the brachial artery and plasma concentration of NO_x (NO₃- and NO2-) were measured, and the mean arterial pressure (MAP), cardiac output (CO), and total vascular conductance (TVC) were assessed at rest and during exercise before and after each treatment. Results: BRJ supplementation significantly increased resting plasma NOx concentrations (123.0±11.3 vs. 181.9±19.5 μM) and the brachial artery FMD (9.8±1.0 vs. 13.5±1.4%) compared to no change after ingestion of the PL. Compared with the PL, BRJ supplementation reduced the MAP (101±1 vs. 99±1 mmHg) at rest and this reduction occurred across workloads, while the TVC was increased only during exercise (p<0.05). There was no difference in CO. 

Conclusions: 15 days of dietary nitrate supplementation could improve endothelial function and contribute to attenuation of an exaggerated exercise BP resulting mainly from a failure to reduce peripheral resistance during exercise.