The Effects of a Single Dose of Concentrated Beetroot Juice on Performance in Trained Flatwater Kayakers

Abstract

The aim of the current study was to determine the effects of dietary nitrate ingestion on parameters of submaximal and supramaximal exercise and time trial (TT) performance in trained kayakers. Eight male kayakers completed four exercise trials consisting of an initial discontinuous graded exercise test to exhaustion and three performance trials using a kayak ergometer. The performance trials were composed of 15 min of paddling at 60% of maximum work rate, five 10-s all-out sprints, and a 1 km TT. The second and third trials were preceded by ingestion of either 70 ml nitrate-rich concentrated beetroot juice (BR) or tomato juice (placebo [PLA]) 3 hr before exercise using a randomized crossover design. Plasma nitrate (PLA: 33.8 ± 1.9 μM, BR: 152 ± 3.5 μM) and nitrite (PLA: 519.8 ± 25.8, BR: 687.9 ± 20 nM) were higher following ingestion of BR compared with PLA (both p < .001). VO2 during steady-state exercise was lower in the BR trial than in the PLA trial (p = .010). There was no difference in either peak power in the sprints (p = .590) or TT performance between conditions (PLA: 277 ± 5 s, BR: 276 ± 5 s, p = .539). Despite a reduction in VO2, BR ingestion appears to have no effect on repeated supramaximal sprint or 1 km TT kayaking performance. A smaller elevation in plasma nitrite following a single dose of nitrate and the individual variability in this response may partly account for these findings.

Acute whole body UVA irradiation combined with nitrate ingestion enhances time trial performance in trained cyclists

“…In this study 8.4 mmol of BR increased plasma nitrite to a greater extent than 4.2 mmol which also coincided with a greater reduction in the oxygen cost of steady-state exercise and improvement in performance. The smaller increase in plasma nitrite following a smaller dose of dietary nitrate or the apparent blunted response in trained athletes compared to recreationally active individuals has been suggested by some authors to be the reason why dietary nitrate supplementation does not improve performance on all occasions (Peacock et al, 2012, Wilkerson et al, 2012, Muggeridge et al, 2013. Nevertheless, we did not observe a correlation between the changes in plasma nitrite and improvement in TT performance in the present study (data not presented).…”

“…We have described the procedures for the determination of nitrite previously (Muggeridge et al, 2013). Briefly, Triiodide reagent was heated in a water bath to 50°C and nitrogen gas bubbled through.…”

“…Conversely, several other studies report exercise performance of varying modalities to be unaltered by dietary nitrate supplementation (Peacock et al, 2012, Wilkerson et al, 2012, Muggeridge et al, 2013. While there are various methodological differences between studies that may account for this disparity, it has become apparent that ergogenic effects appear minimal in highly-trained endurance cohorts (Peacock et al, 2012, Christensen et al, 2013.…”

“…One may, therefore, reasonably assume that elite endurance athletes, who are known to have high proportions of type I muscle fibers, would be less likely to benefit from nitrate supplementation (Andersen et al, 2000). Alternatively, a single low dose of dietary nitrate (~4 -5 mmol) may explain the resultant diminished ergogenic effect of dietary nitrate during some endurance based exercise protocols (Wilkerson et al, 2012, Muggeridge et al, 2013, Wylie et al, 2013a.…”

Dietary nitrate supplementation enhances high-intensity running performance in moderate normobaric hypoxia, independent of aerobic fitness

“…Increasing NO bioavailability via nitrate supplementation has been reported to improve exercise time to exhaustion (TTE) or time-trial (TT) performance in the majority [5,[16][17][18], but not all [23,24] previous investigations in untrained and moderately-trained individuals. Conversely, well-trained participants (V O2max > 60 ml·kg -1 ·min -1 ) are typically less responsive to dietary nitrate supplementation [17,[19][20][21][25][26][27], even when very high nitrate doses (~ 19.5 mmol) are administered [28].…”