Effect of acute dietary nitrate intake on maximal knee extensor speed and power in healthy men and women

Nitric Oxide. 2015 Aug 1;48:16-21. doi: 10.1016/j.niox.2014.08.014. Epub 2014 Sep 6.


Nitric oxide (NO) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle. Dietary nitrate (NO3(-)) intake has been demonstrated to increase NO bioavailability in humans. We therefore hypothesized that acute dietary NO3(-) intake (in the form of a concentrated beetroot juice (BRJ) supplement) would improve muscle speed and power in humans. To test this hypothesis, healthy men and women (n = 12; age = 22-50 y) were studied using a randomized, double-blind, placebo-controlled crossover design. After an overnight fast, subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO3(-). After 2 h, knee extensor contractile function was assessed using a Biodex 4 isokinetic dynamometer. Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole-body NO production. No significant changes in breath NO were observed in the placebo trial, whereas breath NO rose by 61% (P < 0.001; effect size = 1.19) after dietary NO3(-) intake. This was accompanied by a 4% (P < 0.01; effect size = 0.74) increase in peak knee extensor power at the highest angular velocity tested (i.e., 6.28 rad/s). Calculated maximal knee extensor power was therefore greater (i.e., 7.90 ± 0.59 vs. 7.44 ± 0.53 W/kg; P < 0.05; effect size = 0.63) after dietary NO3(-) intake, as was the calculated maximal velocity (i.e., 14.5 ± 0.9 vs. 13.1 ± 0.8 rad/s; P < 0.05; effect size = 0.67). No differences in muscle function were observed during 50 consecutive knee extensions performed at 3.14 rad/s. We conclude that acute dietary NO3(-) intake increases whole-body NO production and muscle speed and power in healthy men and women.

Keywords: Dietary nitrate; Humans; Isokinetic; Muscle power; Nitric oxide.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biological Availability
  • Dietary Supplements
  • Female
  • Humans
  • Knee Joint / drug effects
  • Knee Joint / physiology*
  • Male
  • Middle Aged
  • Muscle Contraction / drug effects
  • Muscle Fatigue / physiology
  • Muscle Strength / physiology
  • Muscle, Skeletal / physiology*
  • Nitrates / administration & dosage
  • Nitrates / pharmacology*
  • Nitric Oxide / pharmacokinetics
  • Torque
  • Young Adult


  • Nitrates
  • Nitric Oxide