Effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance.

Mark Glaister, John R Pattison, Daniel Muniz, Stephen D Patterson, Paul Foley

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)
33 Downloads (Pure)

Abstract

The aim of this study was to examine the acute supplementation effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance. Using a randomized, counterbalanced, double-blind Latin-square design, 14 competitive female cyclists (age: 31 ± 7 years; height: 1.69 ± 0.07 m; body mass: 61.6 ± 6.0 kg) completed four 20-km time trials on a racing bicycle fitted to a turbo trainer. Approximately 2.5 hours before each trial, subjects consumed a 70-ml dose of concentrated beetroot juice containing either 0.45 g of dietary nitrate or with the nitrate content removed (placebo). One hour before each trial, subjects consumed a capsule containing either 5 mg·kg of caffeine or maltodextrin (placebo). There was a significant effect of supplementation on power output (p = 0.001), with post hoc tests revealing higher power outputs in caffeine (205 ± 21 W) vs. nitrate (194 ± 22 W) and placebo (194 ± 25 W) trials only. Caffeine-induced improvements in power output corresponded with significantly higher measures of heart rate (caffeine: 166 ± 12 b·min vs. placebo: 159 ± 15 b·min; p = 0.02), blood lactate (caffeine: 6.54 ± 2.40 mmol·L vs. placebo: 4.50 ± 2.11 mmol·L; p < 0.001), and respiratory exchange ratio (caffeine: 0.95 ± 0.04 vs. placebo: 0.91 ± 0.05; p = 0.03). There were no effects (p ≥ 0.05) of supplementation on cycling cadence, rating of perceived exertion, (Equation is included in full-text article.), or integrated electromyographic activity. The results of this study support the well-established beneficial effects of caffeine supplementation on endurance performance. In contrast, acute supplementation with dietary nitrate seems to have no effect on endurance performance and adds nothing to the benefits afforded by caffeine supplementation.
Original languageEnglish
Pages (from-to)165-174
Number of pages10
JournalJournal of Strength and Conditioning Research
Volume29
Issue number1
DOIs
Publication statusPublished - 29 Jan 2015

Keywords

  • adult
  • Athletic Performance
  • Bicycling
  • Caffeine
  • Dietary Supplements
  • Double-Blind Method
  • Female
  • Heart Rate
  • Humans
  • Nitrates
  • Oxygen Consumption
  • Physical Endurance
  • Physical Exertion
  • Journal Article
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

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