EFFECT OF BEETROOT JUICE INGESTION ON POST-EXERCISE HYPOTENSION AND HEART RATE VARIABILITY IN HYPERTENSIVE POSTMENOPAUSAL WOMEN

Abstract

Objective: To compare the acute effects of a single dose of beet juice (BJ), with different nitrate concentration (NO3-) in post-exercise hypotension (HPE) and in heart rate variability (HRV) in postmenopausal hypertensive women. Design and method: Thirteen hypertensive postmenopausal women (58.1 ± 4.6 years and 27 ± 4 kg/m2) completed the protocol that consisted of three visits with different beverage ingestion in a randomized and crossover design: beetroot juice (BJ) with a high content of nitrate (high-NO3-), BJ with a low content of nitrate (low-NO3-), and an orange flavored non-caloric drink (OFD). After overnight fasting, women drank one of the beverage, rested in siting position for 120 min and then performed 40 min of aerobic exercise at 65–70% of the heat rate (HR) reserve on a treadmill. Blood Pressure (BP) and HR were measured in rest sitting position at 7:20 am (baseline) and during 90 min after exercise. HRV index were analyzed in time (RMSSD, SDNN, PNN50), frequency (HF, LF, LF/HF), and non-linear (SD2, SD1, and SD2/SD1) domains. Two-way ANOVA were used to compare BP and HRV time and sessions responses. Results: No interaction effects (time∗sessions) in BP responses nor any of the HRV indexes after exercise in all among three sessions. However, after aerobic exercise, systolic BP and diastolic BP decreased (p < 0.05), and HRV indexes (LF, LF/HF, SDNN, SD1, SD2, and SD2/SD) increased (p < 0.05) similarly in all three sessions (high-NO3-, low-NO3-, OFD) when compared with the baseline time point. Conclusions: A single dose of BJ, independent of NO3- content, does not change acute aerobic exercise-mediated improvements responses in BP or HRV in hypertensive postmenopausal women.