O efeito de uma dose de suco de beterraba associado ao exercício físico aeróbico na variabilidade da frequência cardíaca de mulheres hipertensas após a menopausa: um estudo cruzado, duplo cego e randomizado

Abstract

The aim of the study was to compare the acute effects of ingesting a dose of beet juice with different concentrations of nitrate, on Heart Rate Variability (HRV) in post-menopausal hypertensive women. Thirteen hypertensive and post-menopausal women (58.1 ± 4.62 years and 27.4 ± 4.25 kg / m2) completed the protocol that consisted of three visits for ingesting different juices in a randomized and crossed order: Beet juice with high content of nitrate (High – NO3-), low nitrate beet juice (Low – NO3-) and orange flavored non-caloric drink (OFD). The volunteers arrived at 7 am in the laboratory and were taken to a room for the analysis of Heart Rate (HR) for 20 minutes. Subsequently, they ingested one of the drinks and remained at rest for two hours until the beginning of the aerobic exercise on a treadmill, which was performed with intensity at 65-70% of the Reserve Heart Rate (FCR) for 40 minutes. After the end of the exercise session, they were again taken to the room and remained for 90 minutes for HR analysis. From the HR data before and after exercise, HRV was calculated for the three sessions in the time (RMSSD, SDNN, Pnn50), frequency (HF, LF, LF / HF) and non-linear (SD2, SD1, SD2 / SD1) domains). The two-way ANOVA showed that there was no difference at any point in the 90 minutes in the HRV domains, for time, SDNN (p = 0.24), RMSSD (p = 0.59) and Pnn50 (p = 0.81), for frequency, LF (p = 0.54), HF (p = 0.80) and LF / HF (p = 0.39) and non-linear domains, being, SD2 (p = 0.55), SD1 (p = 0.10) and SD2 / SD1 (p = 0.46) after the exercise, when comparing the three sessions. Thus, it appears that the intake of beet juice with high or low Nitrate content does not acutely alter the responses of heart rate variability after an aerobic exercise session in postmenopausal hypertensive women.