title: Effect of dietary nitrate supplementation on tolerance to supramaximal intensity intermittent exercise.
abstract: Dietary nitrate (NO3(-)) supplementation has been shown to increase exercise tolerance and improve oxidative efficiency during aerobic exercise in healthy subjects. We tested the hypothesis that a 3-day supplementation in beetroot juice (BJ) rich in NO3(-) would improve the tolerance to supramaximal intensity intermittent exercise consisting of 15-s exercise periods at 170% of the maximal aerobic power interspersed with 30-s passive recovery periods. The number of repetitions completed before reaching volitional exhaustion was significantly higher in the BJ than in the placebo condition (26.1 ± 10.7 versus 21.8 ± 8.0 respectively, P < 0.05). In contrast to previous findings during exercise performed at intensity below the peak oxygen uptake (VO2peak), oxygen uptake (VO2) was unaffected (BJ: 2735 ± 345 mL kg(-1) min(-1) vs. placebo: 2787 ± 346 mL kg(-1) min(-1), NS). However, the Area Under the Curve for microvascular total hemoglobin (AUC-THb) in the vastus lateralis muscle assessed by near infrared spectroscopy during 3 time-matched repetitions was significantly increased with NO3(-) supplementation (BJ: 9662 ± 1228 a.u. vs. placebo:8178 ± 1589 a.u.; P < 0.05). Thus, increased NO3(-) (BJ: 421.5 ± 107.4 μM vs placebo:39.4 ± 18.0 μM) and NO2(-) (BJ: 441 ± 184 nM vs placebo: 212 ± 119 nM) plasma levels (P < 0.001 for both) are associated with improved muscle microvascular Red Blood Cell (RBC) concentration and O2 delivery during intense exercise, despite no effect on resting femoral artery blood flow, and vascular conductance. Maximal voluntary force during an isometric leg extensor exercise, and blood lactate levels were also unaffected by NO3(-) supplementation. To conclude, dietary NO3(-) supplementation enhances tolerance to exercise at supramaximal intensity, with increased microvascular total RBC concentration in the working muscle, in the absence of effect on contractile function and resting hemodynamic parameters.
authors.affiliation: Université Droit et Santé Lille 2, EA7369 Unité de Recherche Pluridisciplinaire Sport, Santé, Société (URePSSS), Equipe "Activité Physique, Muscle, Santé", Faculté des Sciences du Sport et de l'Education Physique, 59790 Ronchin, France. Electronic address: julien.aucouturier@univ-lille2.fr.
authors.forename: Julien
authors.initials: J
authors.lastname: Aucouturier
authors.affiliation: Université Droit et Santé Lille 2, EA7369 Unité de Recherche Pluridisciplinaire Sport, Santé, Société (URePSSS), Equipe "Activité Physique, Muscle, Santé", Faculté des Sciences du Sport et de l'Education Physique, 59790 Ronchin, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Boissière
authors.affiliation: Université Droit et Santé Lille 2, EA7369 Unité de Recherche Pluridisciplinaire Sport, Santé, Société (URePSSS), Equipe "Activité Physique, Muscle, Santé", Faculté des Sciences du Sport et de l'Education Physique, 59790 Ronchin, France.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Pawlak-Chaouch
authors.affiliation: Haute Ecole Provinciale de Hainaut-Condorcet, Tournai, Belgium.
authors.forename: Grégory
authors.initials: G
authors.lastname: Cuvelier
authors.affiliation: Université Droit et Santé Lille 2, EA7369 Unité de Recherche Pluridisciplinaire Sport, Santé, Société (URePSSS), Equipe "Activité Physique, Muscle, Santé", Faculté des Sciences du Sport et de l'Education Physique, 59790 Ronchin, France.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Gamelin
mesh_terms: D000328:Adult; D027461:Beta vulgaris; D001628:Beverages; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D019587:Dietary Supplements; D017079:Exercise Tolerance / Q000187:drug effects*; D006801:Humans; D008297:Male; D009566:Nitrates / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects*; D011897:Random Allocation; D055815:Young Adult
chemical_list: D009566:Nitrates
keywords: Exercise; Nitrate; Tolerance