How beetroot helps to exercise longer?

 Drinking beetroot juice helped increase blood flow to muscles, which led to

1. greater oxygen delivery
2. less fatigue during exercise.

Competitive cyclists who supplemented with beetroot juice improved their performance by 0.8 percent in a 50-mile test.

Significant improvements were observed during the last 10 miles.

Both oxygen efficiency and time to exhaustion were greatly improved after beet juice consumption.