Researchers at Appalachian State University in North Carolina tested 20 young men, dividing them into two groups. Half received an antioxidant supplement for two weeks and half didn't. The benefits from antioxidants were remarkable.
The researchers found that taking the antioxidant supplement allowed blood pressure to normalize faster after 30 minutes of intense exercise. The men taking the supplement also had an "augmentation index" that was nearly four times lower, showing that their arteries were far more flexible. (A high augmentation index is a risk factor for a heart attack.)
The bottom line is that if you have high blood pressure, maximizing your blood level of antioxidants is very important (I recommend taking a good multivitamin powder that is loaded with antioxidants).
"The effects of a multiflavonoid supplement on vascular and hemodynamic parameters following acute exercise." Kappus RM, et al., Oxidation Medicine and Cell Longevity, 2011;2011:210798. Epub 2011 Dec 4.