title: Effects of nitrate on the power-duration relationship for severe-intensity exercise.
abstract: OBJECTIVE
  The power asymptote (critical power [CP]) and curvature constant (W') of the power-duration relationship dictate the tolerance to severe-intensity exercise. We tested the hypothesis that dietary nitrate supplementation would increase the CP and/or the W' during cycling exercise.
  
  
  METHODS
  In a double-blind, randomized, crossover study, nine recreationally active male subjects supplemented their diet with either nitrate-rich concentrated beetroot juice (BR; 2 × 250 mL·d, ∼8.2 mmol·d nitrate) or a nitrate-depleted BR placebo (PL; 2 × 250 mL·d, ∼0.006 mmol·d nitrate). In each condition, the subjects completed four separate severe-intensity exercise bouts to exhaustion at 60% of the difference between the gas exchange threshold and the peak power attained during incremental exercise (60% Δ), 70% Δ, 80% Δ, and 100% peak power, and the results were used to establish CP and W'.
  
  
  RESULTS
  Nitrate supplementation improved exercise tolerance during exercise at 60% Δ (BR, 696 ± 120 vs PL, 593 ± 68 s; P < 0.05), 70% Δ (BR, 452 ± 106 vs PL, 390 ± 86 s; P < 0.05), and 80% Δ (BR, 294 ± 50 vs PL, 263 ± 50 s; P < 0.05) but not 100% peak power (BR, 182 ± 37 vs PL, 166 ± 26 s; P = 0.10). Neither CP (BR, 221 ± 27 vs PL, 218 ± 26 W) nor W' (BR, 19.3 ± 4.6 vs PL, 17.8 ± 3 kJ) were significantly altered by BR.
  
  
  CONCLUSIONS
  Dietary nitrate supplementation improved endurance during severe-intensity exercise in recreationally active subjects without significantly increasing either the CP or the W'.
authors.affiliation: College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors.forename: James
authors.initials: J
authors.lastname: Kelly
authors.forename: Anni
authors.initials: A
authors.lastname: Vanhatalo
authors.forename: Daryl P
authors.initials: DP
authors.lastname: Wilkerson
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Wylie
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D000328:Adult; D027461:Beta vulgaris; D001642:Bicycling / Q000502:physiology; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D017079:Exercise Tolerance / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D009566:Nitrates / Q000494:pharmacology*; D010807:Physical Endurance / Q000187:drug effects* / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D010936:Plant Extracts / Q000494:pharmacology*; D018517:Plant Roots; D055815:Young Adult
chemical_list: D009566:Nitrates; D010936:Plant Extracts