Journal de recherche en science de la nutrition

Abstrait

Acute Dose of Beet Root Juice Does Not Improve Endurance Performance in Elite Triathletes

Logan-Sprenger HM and Logan SL

The aim of this study was to investigate whether consuming a high acute dose of NO3 -rich beetroot juice (BRJ) results in a significant (A) increase in plasma nitrite (NO2 -), and; (B) improvement in exercise performance during a 30 min time trial (TT) among competitive elite triathletes. Eight triathletes (4 females, 4 males; age 22 ± 0.9 yrs) participated in this study. (A) Baseline (PRE) venous blood samples were taken. Subjects then consumed 210 mL (19.4 mmol NO3 -) of BRJ and a second blood sample was taken 2.5 hr after consumption (POST) and blood samples were analyzed for [NO2 -]. (B) Seven days later, in a randomized, single-blinded, crossover design, subjects completed two laboratory-based 30 min TT separated by 7 days. 2.5 hr prior the TT, subjects consumed either BRJ or a nitrate-free BRJ placebo (PL). (A) Plasma [NO2 -] did not significantly change from baseline values after consuming 210 mL of BRJ (PRE: 1.62 ± 0.17 uM, POST: 1.76 ± 0.15 uM). (B) In response to BRJ supplementation, there was no significant difference over the TT in mean power output (BRJ: 4.19 ± 0.2 W/kg, PL: 4.23 ± 0.2 W/ kg), distance covered (BRJ: 16.1 ± 0.6 km, PL: 16.2 ± 0.7 km), or average speed (PL: 32.4 ± 1.4; BRJ: 32.6 ± 1.3 kph). Further, when the subjects were separated into BRJ ‘responders’ and ‘non-responders’ we did not observe statistically significant changes in any of the performance measures between the PL and BRJ supplementation. In conclusion, there is no ergogenic benefit to supplementing elite athletes with an acute dose of BRJ prior to a high intensity middle-distance cycling competition.