Supervisors info:
Κοσκολού Μ., Αναπληρώτρια Καθηγήτρια, ΣΕΦΑΑ, ΕΚΠΑ
Γιαννακούλια Μ., Καθηγήτρια, Τμήμα Διαιτολογίας και Διατροφής, Χαροκόπειο Παν/μιο
Γελαδάς Ν., Καθηγητής Εργοφυσιολογίας, ΣΕΦΑΑ, ΕΚΠΑ
Summary:
INTRODUCTION
A continuing effort to discover more and more effective performance-enhancers,
combined with the need to turn to natural substances, are perhaps some of the reasons
that, in recent years, have led to the emergence of beetroot juice as an ergogenic
supplement, the spread of which is growing on research level, as well as in sports
practice. With its precise mechanisms of action being not fully elucidated yet, it is
considered certain that the natural nitrate content of beetroot plays a key role. When
entering the body beetroot nitrate is reduced to nitric oxide, which as an active signaling
molecule and it is able, even after a single dose of the supplement, to modify normal
responses during exercise, affecting performance. Despite the extensive study that has
shown the effect of beetroot juice on different types of exercise and among different
population groups, research on women remains insufficient. This fact, combined with
research data showing differences in nitrogen monoxide metabolism between men and
women, necessitates designing an experimental study of the effect of beetroot juice on
normal exercise responses in women only. The purpose of this study was to examine the
effect of beetroot juice on physiological responses during exercise (submaximal,
gradually increasing intensity to exhaustion and sprinting), exclusively in women. The
effect of beetroot juice on blood pressure pre- and post-exercise as well as the relationship
btween hematocrit and the effect of beetroot on performance during maximal work were
also investigated.
METHOD
Six female subjects of reproductive age and moderate training level participated in the
study. After undergoing body measurements and ergometric tests to evaluate their athletic
profile, they performed a protocol with three types of exercise (sub-maximal work,
sprinting, and incremental exercise to exhaustion), 150 minutes after ingestion of beetroot
juice (6-7 mmol nitrate). At the next session, they performed an identical exercise
protocol following acute placebo administration. All measurements were conducted
between mean luteal and the beginning of the next ovarian phase of the subjects’ cycle.
Hematocrit, blood pressure (at rest before and after beetroot juice administration and
post-exercise), heart rate and respiratory gases (throughout the exercise protocol) as well
as the power output were measured. Statistical analysis was performed using t-test, 2-way
ANOVA for repeated measurements with Bonferroni correction, and Pearson’s r
correlation. The level of statistical significance was set at a = 0.05.
RESULTS
The difference in blood pressure 150 minutes after ingesting beetroot juice from baseline
values (time 0) (ΔBP = BP150'-BP0 ') did not show a significant difference between the beetroot juice (ΔSBP = -0,09 ± 3,09, ΔDBP = 1 , 33 ± 3.82) and placebo (ΔSBP = 3.17 ±
3.49, ΔDBP = 3.75 ± 4.30) conditions, for both systolic (p = 0.259) and diastolic pressure
(p = 0.369), while for mean blood pressure (DΜBP BRJ =0.87±3.43, DΜBP PL =4.90±1.86)
the difference was marginally not significant (p = 0.068). The mean oxygen consumption
during sub-maximal work did not differ (p = 0.276) after the ingestion of beetroot juice
(25.06 ± 2.06 ml / kg / min) and placebo (25.77 ± 3.09 ml / kg / min). No significant
relationship was found between hematocrit and oxygen uptake at submaximal work
(p=0.754). Maximal power at the sprint in the beetroot condition (Pmax = 577.9 ± 76.32
Watt) also did not differ significantly (p = 0.235) compared to the placebo condition
(Pmax = 563.96 ± 109.18 Watt). In the exercise test of gradually increasing intensity to
exhaustion, both maximal oxygen consumption (VO 2 peak) and maximal power (Ppeak)
did not differ significantly between conditions (p = 0.691; p = 0.235), but maximal heart
rate (HR) was significantly higher in the beetroot juice condition (179 ± 12.65 bpm)
compared to the placebo condition (176.8 ± 12.56 bpm) (p = 0.029). Finally, there was no
significant difference in post-exercise blood pressure between the two conditions (p treatment =
0.138, p timextreatment =0.492).
CONCLUSION
The present study did not show statistically significant differences between beetroot juice
and placebo conditions in most parameters examined. The statistically significantly
higher maximal heart rate at the end of the incremental exercise protocol combined with
the strong tendency for maintainace of mean blood pressure after beetroot ingestion as
compared to the placebo condition could suggest a compensatory reaction of the body
against reduction of total peripheral resistance elicited by nitric oxide acting as
vasodilator. It is possible that beetroot juice ingestion led to improved baroreceptor
sensitivity, increasing the range of positive heart rate response during exercise.
Nevertheless, further research is needed with a larger sample in order to draw safer
conclusions on this topic.
Keywords:
beetroot juice, nitrates, blood pressure, submaximal work, sprint, post- hypotensive hypotension, normal responses, women.
