Purpose: Dietary nitrate supplementation has been shown to reduce the O2 cost of submaximal exercise and to improve high-intensity exercise tolerance. However, it is presently unknown whether it may enhance performance during simulated competition. The present study investigated the effects of acute dietary nitrate supplementation on power output (PO), V˙O2, and performance during 4- and 16.1-km cycling time trials (TT).
Methods: After familiarization, nine club-level competitive male cyclists were assigned in a randomized, crossover design to consume 0.5 L of beetroot juice (BR; containing ∼6.2 mmol of nitrate) or 0.5 L of nitrate-depleted BR (placebo, PL; containing ∼0.0047 mmol of nitrate), ∼2.5 h before the completion of a 4- and a 16.1-km TT.
Results: BR supplementation elevated plasma [nitrite] (PL = 241 ± 125 vs BR = 575 ± 199 nM, P < 0.05). The V˙O2 values during the TT were not significantly different between the BR and PL conditions at any elapsed distance (P > 0.05), but BR significantly increased mean PO during the 4-km (PL = 279 ± 51 vs BR = 292 ± 44 W, P < 0.05) and 16.1-km TT (PL = 233 ± 43 vs BR = 247 ± 44 W, P < 0.01). Consequently, BR improved 4-km performance by 2.8% (PL = 6.45 ± 0.42 vs BR = 6.27 ± 0.35 min, P < 0.05) and 16.1-km performance by 2.7% (PL = 27.7 ± 2.1 vs BR = 26.9 ± 1.8 min, P < 0.01).
Conclusions: These results suggest that acute dietary nitrate supplementation with 0.5 L of BR improves cycling economy, as demonstrated by a higher PO for the same V˙O2 and enhances both 4- and 16.1-km cycling TT performance.
1Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Exeter, UNITED KINGDOM; and 2Peninsula College of Medicine and Dentistry, St. Luke's Campus, University of Exeter, Exeter, UNITED KINGDOM
Address for correspondence: Andrew M. Jones, Ph.D., Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, EX1 2LU, United Kingdom; E-mail: firstname.lastname@example.org.
Submitted for publication November 2010.
Accepted for publication February 2011.