Effects of beetroot juice intake on repeated performance of competitive swimmers

Beetroot juice is a sport supplement with a high level of evidence on the physical performance enhancement. However, in swimming, there is no clear data about the effects of beetroot juice on performance. To investigate whether an acute intake of beetroot juice (BJ) improves the performance of competitive swimmers in a repeated maximum swimming effort. Thirteen national-level swimmers (six females and seven males), participated in this randomized, double-blind crossover study. In two different trials, swimmers ingested a 70-mL placebo shot (.04 mmol NO ; PLA) or a 70-mL Beet-It shot (6.4 mmol of NO beet juice [BJ]) 3 h before undergoing a 6 × 100-m front-crawl maximal effort test with 7 min rest between each 100 m. Overall, 100-m times showed no difference between the BJ and PLA groups ( = .364), although a possibly shorter time was observed for BJ in the last repetition ( = .104; mean difference [MD] = -.99 s, mean-based inference [MBI] = 49/51/0). Participants in the BJ condition showed a possibly lower rate of perceived exertion in the first ( = .242, MD = -.85, MBI = 70/28/2) and second repetitions ( = .165, MD = 1.15, MBI = 83/16/1), whereas Total Quality Recovery scale scores were likely higher in the first ( = .110, MD = 1.15, MBI = 83/16/1) and third ( = .082, MD = -.77, MBI = 70/29/1) repetitions compared with those in the PLA group. Blood lactate concentration [La ] levels showed no differences between groups in any of the repetitions ( > .05, unclear), and we observed an increase in 100-m times for both BJ and PLA (BJ: = .014, MD = -1.51 s; PLA: = .029, MD = -1.57 s) after the fifth repetition. No clear differences in performance were observed in a 6 × 100-m repeated sprint test by competitive swimmers when supplementing (or not) with BJ. However, there was a trend toward a better recovery between efforts and a better tolerance of fatigue when swimmers ingested BJ.