Author(s): Cermak NM, Gibala MJ
Six days of dietary nitrate supplementation in the form of beetroot juice (~0.5 L/d) has been reported to reduce pulmonary oxygen uptake (VO₂) during submaximal exercise and increase tolerance of high-intensity work rates, suggesting that nitrate can be a potent ergogenic aid. Limited data are available regarding the effect of nitrate ingestion on athletic performance, and no study has investigated the potential ergogenic effects of a small-volume, concentrated dose of beetroot juice. The authors tested the hypothesis that 6 d of nitrate ingestion would improve time-trial performance in trained cyclists. Using a double-blind, repeated-measures crossover design, 12 male cyclists (31±3 yr, VO2peak=58±2 ml·kg⁻¹·min⁻¹, maximal power [Wmax]=342±10 W) ingested 140 ml/d of concentrated beetroot (~8 mmol/d nitrate) juice (BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) for 6 d, separated by a 14-d washout. After supplementation on Day 6, subjects performed 60 min of submaximal cycling (2×30 min at 45% and 65% Wmax, respectively), followed by a 10-km time trial. Time-trial performance (953±18 vs. 965±18 s, p<.005) and power output (294±12 vs. 288±12 W, p<.05) improved after BEET compared with PLAC supplementation. Submaximal VO₂ was lower after BEET (45% Wmax=1.92±0.06 vs. 2.02±0.09 L/min, 65% Wmax 2.94±0.12 vs. 3.11±0.12 L/min) than with PLAC (main effect, p<.05). Whole-body fuel selection and plasma lactate, glucose, and insulin concentrations did not differ between treatments. Six days of nitrate supplementation reduced VO₂ during submaximal exercise and improved time-trial performance in trained cyclists.