Dose response of nitrate supplementation on 2000m rowing ergometer performance

Introduction: Beetroot juice is a naturally rich source of nitrate (NO3-), a compound hypothesized to enhance endurance performance by improving exercise efficiency. This study investigated the effect of multiple doses of beetroot juice on 2000m ergometer rowing performance in well trained athletes. Methods: Ten highly trained male rowers (17±3.4 h training per week) volunteered to participate in a counterbalanced, placebo controlled, cross-over study. Subjects were given either 0mmol (PLACEBO), 4.2mmol (SINGLE) or 8.4mmol (DOUBLE) NO3- via a beetroot juice supplement 2 h before undertaking a 2000mtest on a rowing ergometer. Blood samples were taken before supplement ingestion and immediately before the rowing test for later analysis of plasma [NO3-] and [nitrite (NO2-)]. Results: The SINGLE dose demonstrated a trivial effect compared to PLACEBO on 2000m time to completion. A possibly beneficial effect of DOUBLE was found compared to SINGLE (mean difference: -1.8±2.1 s) and PLACEBO (-1.6±1.6 s) respectively. Plasma [NO2-] and [NO3-] demonstrated a dose-response effect, with greater amounts of nitrate ingested leading to substantially higher concentrations (DOUBLE > SINGLE > PLACEBO). There was a moderate but insignificant positive correlation (r = 0.573, p = 0.065) between change in plasma [NO2-] and improvement in performance. Conclusion: When compared with placebo, a high (8.4mmol NO3-) but not moderate (4.2mmol NO3-) dose of beetroot juice 2 h before exercise improved 2000mrowing performance in highly trained athletes.