Fig 1.
CONSORT recruitment diagram for enrolment and study completion.
Table 1.
Demographic and baseline clinical characteristics of the subjects (n = 21).
Fig 2.
Alterations in plasma nitrate following dosing.
Plasma nitrate concentrations prior to (‘baseline’) and following consumption of a nitrate-rich or placebo beverage. ‘Post dosing’ indicates a time point 3 hours following consumption which was immediately prior to cardiopulmonary exercise testing. ‘Peak’ was a time point at the point of exhaustion during endurance cycle ergometry testing. Repeated measures analysis of variance (ANOVA) was used to compare plasma nitrate metabolites between treatment conditions and at each specific time-point; *significantly different from baseline, p<0.0001; †significantly different from placebo group, p<0.0001.
Fig 3.
Endurance time during cycle ergometry at 70% maximal workload measured in the placebo and nitrate-rich beetroot juice dosing conditions.
A Wilcoxon test was used to compare median values in the two treatment groups; no significant difference was found.
Fig 4.
Blood pressure parameters following dosing.
Alterations in blood pressure parameters (systolic blood pressure sBP, diastolic blood pressure dBP and mean arterial pressure MAP) relative to presupplemented baseline 3 hours following dosing with nitrate-rich beetroot juice or placebo preparation. Paired t-tests were used to compare blood pressure parameters between treatment groups; *significantly different from placebo, p<0.01.
Table 2.
Rest and isotime analysis of the cardiopulmonary exercise test parameters.
Fig 5.
The graph represents the VO2 at each 10th percentile of isotime with 0% representing the initiation of loaded cycling at 70% maximal workload achieved on incremental cycle ergometry. The area under the curves to isotime was compared using a paired t-test showing significant separation of the curves representing the two treatment conditions (p = 0.027).
Fig 6.
Individual responses for area under the curve (AUC) to VO2 isotime.
There was a significant difference between the two treatment conditions with a reduction in the area of the curve to VO2 isotime in the nitrate supplemented condition.
Fig 7.
Alteration in plasma metabolomics during endurance cycle ergometry.
Values are expressed as a ratio of peak exercise:pre exercise, with a value of 1 indicative of no change. Paired t-tests were utilised to compare metabolite levels between treatment conditions, with no significant difference seen for any metabolite analysed.