Resumen de No Improvement in Endurance Performance After a Single Dose of Beetroot Juice
Naomi M. Cermak, Peter Res, Rudi Stinkens, Jon O. Lundberg, Martin J. Gibala, Luc J.C. van Loon
Introduction: Dietary nitrate supplementation has received much attention in the literature due to its proposed ergogenic properties. Recently, the ingestion of a single bolus of nitrate-rich beetroot juice (500 ml, ~6.2 mmol NO3�) was reported to improve subsequent time-trial performance. However, this large volume of ingested beetroot juice does not represent a realistic dietary strategy for athletes to follow in a practical, performancebased setting. Therefore, we investigated the impact of ingesting a single bolus of concentrated nitrate-rich beetroot juice (140 ml, ~8.7 mmol NO3�) on subsequent 1-hr time-trial performance in well-trained cyclists. Methods: Using a double-blind, repeated-measures crossover design (1-wk washout period), 20 trained male cyclists (26 ± 1 yr, VO2peak 60 ± 1 ml · kg�1 · min�1, Wmax 398 ± 7.7 W) ingested 140 ml of concentrated beetroot juice (8.7 mmol NO3�; BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) with breakfast 2.5 hr before an ~1-hr cycling time trial (1,073 ± 21 kJ). Resting blood samples were collected every 30 min after BEET or PLAC ingestion and immediately after the time trial. Results: Plasma nitrite concentration was higher in BEET than PLAC before the onset of the time trial (532 ± 32 vs. 271 ± 13 nM, respectively; p < .001), but subsequent time-trial performance (65.5 ± 1.1 vs. 65 ± 1.1 s), power output (275 ± 7 vs. 278 ± 7 W), and heart rate (170 ± 2 vs. 170 ± 2 beats/min) did not differ between BEET and PLAC treatments (all p > .05). Conclusion: Ingestion of a single bolus of concentrated (140 ml) beetroot juice (8.7 mmol NO3�) does not improve subsequent 1-hr time-trial performance in well-trained cyclists.
