We tested the hypothesis that exaggerated pressor responses observed in prehypertensive males (N = 9) during dynamic exercise are attenuated following acute dietary supplementation with grape seed extract (GSE) (i.e., a single dose). Effects of placebo and GSE (300 mg) on systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), cardiac output (CO), stroke volume (SV), total vascular conductance (TVC), and rate × pressure product (RPP) in response to two submaximal cycling workloads (40% and 60% VO2peak) were compared 2 h after ingestion of GSE or placebo on different days, 1 week apart. Endothelial function was also evaluated using flow-mediated dilation (FMD). Placebo treatment had no effect on any of the variables. GSE supplementation attenuated MAP at both workloads (40% VO2peak: 115 ± 1 vs. 112 ± 2 mmHg; 60% VO2peak: 126 ± 2 vs. 123 ± 2 mmHg) and RPP at the lower workload. Conversely, SV, CO, and TVC were augmented during both workloads. FMD was augmented by GSE (18.9 ± 2.0 vs. 12.4% ± 2.0%). These findings indicate that in exercising prehypertensive males, a single dose of GSE reduces blood pressure, peripheral vasoconstriction, and work of the heart and enhances O2 delivery; effects that may be due, in part, to endothelium-dependent vasodilation. We propose that acute GSE treatment represents an intervention that may minimize potential increases in the risk of cardiovascular events during dynamic exercise in prehypertensives.
