Effect of beetroot juice supplementation on 10-km performance in recreational runners.

The purpose of this study was to investigate the effects of chronic beetroot juice (BRJ) supplementation on 10-km running performance in recreational runners. In a double-blind, placebo-controlled, crossover-designed study, 14 male recreational runners (age, 27.8 ± 3.4 years) performed three 10-km running tests, at baseline and under the conditions of BRJ supplementation and placebo (PLA). Supplementation was administered for 3 days, and on the days of the assessments, the ingestion occurred 2 h before the test and consisted of a dose of 420 mL of BRJ in natura (8.4 mmol inorganic nitrate (NO)·day) or PLA with depleted NO (0.01 mmol NO·day). The mean velocity (MV) was calculated, and the following variables were determined: maximal heart rate, maximal rating of perceived exertion blood glucose concentration (analyzed before and after the test), and lactate peak. There was no main effect between conditions regarding 10-km running time performance (BRJ: 50.1 ± 5.3 min; PLA: 51.0 ± 5.1 min; P = 0.391) and total MV (BRJ: 12.1 ± 1.3 km·h; PLA: 11.9 ± 1.2 km·h; P = 0.321) or in the other analyzed variables. The time to complete the first half of the test (5 km) was statistically lower in the BRJ group than in the PLA group (P = 0.027). In conclusion, chronic supplementation with BRJ increased MV in the first half of the test and improved the final test times of 10 of the 14 runners, although we did not find a statistically significant difference in the performance of the 10-km run.