Abstract
As a nitric oxide precursor, beetroot juice (BJ) is known to enhance high-intensity exercise performance (80–100% VO2max) yet its impacts on higher intensity sprint exercise (>100% VO2max) remain to be established. This study sought to examine the effects of BJ supplementation on performance and subsequent fatigue during an all-out sprint exercise. Using a randomized cross-over, double-blind, placebo-controlled design, 15 healthy resistance-trained men (22.4 ± 1.6 years) ingested 70 mL of either BJ or placebo. Three hours later, participants undertook a 30-s all-out Wingate test. Before and after the sprint exercise and at 30 s and 180 s post-exercise, three countermovement jumps (CMJ) were performed and blood lactate samples were obtained. Compared to placebo, BJ consumption improved peak (placebo vs. BJ, 848 ± 134 vs. 881 ± 135 W; p = 0.049) and mean (641 ± 91 vs. 666 ± 100 W; p = 0.023) power output and also reduced the time taken to reach Wpeak in the Wingate test (8.9 ± 1.4 vs. 7.3 ± 0.9 s; p = 0.003). No differences were detected in the fatigue index. In addition, while over time CMJ height and power diminished (ANOVA p < 0.001) and blood lactate levels increased (ANOVA p < 0.001), no supplementation effect was observed. Our findings indicate that while BJ supplementation improved performance at the 30-s cycling sprint, this improvement was not accompanied by differences in fatigue during or after this type of exercise.
Highlights
Dietary nitrate supplementation has been described as a potential ergogenic aid for high-intensity exercise efforts (80–100% VO2max ) as it reduces the oxygen cost of ATP synthesis and ATP
No significant differences were observed in Wmin (~4.4%; p = 0.064) or fatigue index (FI) (~0.22%; p = 0.914)
beetroot juice (BJ) supplementation overall did not give rise to a greater fatigue index during the second half of the test or to neuromuscular fatigue as measured in countermovement jumps (CMJ) tests, after the 30-s all-out sprint test. These results indicate that the improved sprint performance induced by BJ as a NO3 − -rich supplement may not be accompanied by more fatigue
Summary
Dietary nitrate supplementation has been described as a potential ergogenic aid for high-intensity exercise efforts (80–100% VO2max ) as it reduces the oxygen cost of ATP synthesis and ATP cost of muscle contraction improving muscle contraction/relaxation, force and power production [1,2,3]. Of circulating NO3 − is taken up by salivary gland acinar cells in a process facilitated by sialin [8,9] Oral microorganisms, those on the posterior aspect of the tongue, initiate the reduction of NO3 −. NO offers several exercise adaptation benefits [11] through its effects of inducing vasodilatation, reducing blood viscosity, and promoting muscular oxygen perfusion and gas exchange [12]. NO it is able to increase force and power production during muscle contraction, decreasing the cost of ATP needed as well as the oxygen required to synthesize ATP [1,2,3]
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