title: Inorganic nitrate supplementation improves muscle oxygenation, O₂ uptake kinetics, and exercise tolerance at high but not low pedal rates.
abstract: We tested the hypothesis that inorganic nitrate (NO3 (-)) supplementation would improve muscle oxygenation, pulmonary oxygen uptake (V̇o2) kinetics, and exercise tolerance (Tlim) to a greater extent when cycling at high compared with low pedal rates. In a randomized, placebo-controlled cross-over study, seven subjects (mean ± SD, age 21 ± 2 yr, body mass 86 ± 10 kg) completed severe-intensity step cycle tests at pedal cadences of 35 rpm and 115 rpm during separate nine-day supplementation periods with NO3 (-)-rich beetroot juice (BR) (providing 8.4 mmol NO3 (-)/day) and placebo (PLA). Compared with PLA, plasma nitrite concentration increased 178% with BR (P < 0.01). There were no significant differences in muscle oxyhemoglobin concentration ([O2Hb]), phase II V̇o2 kinetics, or Tlim between BR and PLA when cycling at 35 rpm (P > 0.05). However, when cycling at 115 rpm, muscle [O2Hb] was higher at baseline and throughout exercise, phase II V̇o2 kinetics was faster (47 ± 16 s vs. 61 ± 25 s; P < 0.05), and Tlim was greater (362 ± 137 s vs. 297 ± 79 s; P < 0.05) with BR compared with PLA. These results suggest that short-term BR supplementation can increase muscle oxygenation, expedite the adjustment of oxidative metabolism, and enhance exercise tolerance when cycling at a high, but not a low, pedal cadence in healthy recreationally active subjects. These findings support recent observations that NO3 (-) supplementation may be particularly effective at improving physiological and functional responses in type II muscle fibers.
authors: Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK; s.j.bailey@exeter.ac.uk.
authors: Stephen J
authors: SJ
authors: Bailey
authors: Sport and Health Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford, UK;
authors: Richard L
authors: RL
authors: Varnham
authors: Teachers College, Department of Biobehavioral Sciences, Columbia University, New York, New York; and.
authors: Fred J
authors: FJ
authors: DiMenna
authors: School of Biological and Biomedical Sciences, Plymouth University, Plymouth, UK.
authors: Brynmor C
authors: BC
authors: Breese
authors: Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK;
authors: Lee J
authors: LJ
authors: Wylie
authors: Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK;
authors: Andrew M
authors: AM
authors: Jones
mesh_terms: D027461:Beta vulgaris; D001642:Bicycling; D018592:Cross-Over Studies; D019587:Dietary Supplements; D015444:Exercise; D017079:Exercise Tolerance / Q000187:drug effects; D000067030:Fruit and Vegetable Juices; D006801:Humans; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D018763:Muscle Fatigue / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009566:Nitrates / Q000008:administration & dosage*; D010101:Oxygen Consumption / Q000187:drug effects*; D058573:Performance-Enhancing Substances / Q000008:administration & dosage*; D018517:Plant Roots; D055815:Young Adult
chemical_list: D009566:Nitrates; D058573:Performance-Enhancing Substances
keywords: exercise performance; fatigue; nitric oxide; oxidative metabolism; vascular function