Beetroot & HRV

The effects of a beetroot extract on heart rate variability (HRV) recovery following strength-based exercises were recently assessed in 12 healthy adult males via a randomized double-blind and placebo-controlled trial. Participants received either placebo or 600 mg beetroot extract, followed by 2 hours of rest to allow for digestion/absorption. Four sets of each strength-based exercise were then performed (leg press 45 degrees, extender chair, abductor chair, and squat, all done at 75% of 1 repetition maximum test), with measurements of blood pressure, heart rate, and various HRV indexes taken before and multiple times in the 1 hour post-exercise.

Given the metabolic demands of exercise, it is expected that sympathetic activity would increase in response to the additional load, and that parasympathetic activity would be withdrawn, observable by a drop in HRV. The time to HRV recovery following exercise can be used as a marker for recovery of the cardiovascular system, to help prevent overloading or excessive levels of exercise (as well as predicting the cardiovascular fitness of the participant). 

In this study, the men receiving beetroot had faster recovery of systolic blood pressure (SBP), heart rate, and HRV when compared to placebo. For example, the geometric indices of HRV (SD1 and SD2) recovered by 30-35 minutes in the beetroot group, vs. 50-55 minutes in the placebo group. Similar results were observed in a placebo-controlled trial which enrolled young healthy African American women, in which beetroot juice was shown to decrease SBP and increase HRV, both at rest and during aerobic exercise. Thus, both of these studies suggest improved cardiovascular and autonomic recovery following exercise, potentially limiting exercise-induced cardiovascular complications.