A recent study that was published in American Journal of Physiology- Regulatory, Integrative and Comparative Physiology showed that beet juice not only lower blood pressure but if used on a regular basis, it can improve exercise performance in relation to muscle oxygen delivery and the heart's work load during exercise.
It was already documented by American Heart Association’s Journal Hypertension that drinking a cup of beet juice a day can lower blood pressure by 7 percent.
The new research included 14 healthy adult males who consumed either a nitrate rich beet juice or a nitrate depleted beet juice. For 15 days the participants were closely monitored and the blood pressure readings were documented.
The results of the study showed that the test subjects that consumed the nitrate rich beet juice had more dilated blood vessels during exercise and at rest, thus they had lower blood pressure. The subjects that consumed the nitrate rich beet juice also experienced better vessel dilation during exercise which made the heart more efficient and use less oxygen. Additional to nitrates decreasing the heart's work load it also improved oxygen delivery to the muscles.
Source: Choi H, Chang M, Kim J, Nho H, Jung E, Stebbins C, Lee J. Effects of Chronic Dietary Nitrate Supplementation on the Hemodynamic Response to Dynamic Exercise. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2015.