title: l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans.
abstract: The purpose of this study was to compare the effects of l-citrulline (Cit) and l-arginine (Arg) supplementation on nitric oxide (NO) biomarkers, pulmonary O2 uptake (V̇o2) kinetics, and exercise performance. In a randomized, placebo (Pla)-controlled, crossover study, 10 healthy adult men completed moderate- and severe-intensity cycling exercise on days 6 and 7 of a 7-day supplementation period with Pla, Arg (6 g/day), and Cit (6 g/day). Compared with Pla, plasma Arg concentration was increased by a similar magnitude with Arg and Cit supplementation, but plasma Cit concentration was only increased (P < 0.001) with Cit supplementation. Plasma nitrite (NO2 (-)) concentration was increased with Arg supplementation (P < 0.05) and tended to increase with Cit supplementation (P = 0.08) compared with Pla (83 ± 25, 106 ± 41, and 100 ± 38 nM with Pla, Arg, and Cit, respectively); however, mean arterial blood pressure was only lower (P < 0.05) after Cit supplementation. The steady-state V̇o2 amplitude during moderate-intensity cycle exercise was not significantly different between supplements, but Cit lowered the V̇o2 mean response time (59 ± 8 and 53 ± 5 s with Pla and Cit, respectively, P < 0.05) during severe-intensity exercise, improved tolerance to severe-intensity exercise (589 ± 101 and 661 ± 107 s with Pla and Cit, respectively), and increased the total amount of work completed in the exercise performance test (123 ± 18 and 125 ± 19 kJ with Pla and Cit, respectively, P < 0.05). These variables were not altered by Arg supplementation (P > 0.05). In conclusion, these results suggest that short-term Cit, but not Arg, supplementation can improve blood pressure, V̇o2 kinetics, and exercise performance in healthy adults.
authors.affiliation: Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and S.J.Bailey@exeter.ac.uk.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Bailey
authors.affiliation: Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and.
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Blackwell
authors.affiliation: Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and.
authors.forename: Terrence
authors.initials: T
authors.lastname: Lord
authors.affiliation: Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and.
authors.forename: Anni
authors.initials: A
authors.lastname: Vanhatalo
authors.affiliation: Exeter Medical School, St. Luke's Campus, University of Exeter, Exeter, United Kingdom.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Winyard
authors.affiliation: Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, United Kingdom; and.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D001120:Arginine / Q000008:administration & dosage* / Q000097:blood; D001642:Bicycling; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D002956:Citrulline / Q000008:administration & dosage* / Q000097:blood; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D004739:England; D015444:Exercise; D017079:Exercise Tolerance / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects*; D058573:Performance-Enhancing Substances / Q000008:administration & dosage* / Q000097:blood; D019265:Spectroscopy, Near-Infrared; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D015415:Biomarkers; D058573:Performance-Enhancing Substances; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine
keywords: blood pressure; fatigue; metabolism; near-infrared spectroscopy; nitric oxide