This study examined the effects of beetroot juice (BTJ) on recovery between two repeated-sprint tests. In an independent groups design, 20 male, team-sports players were randomized to receive either BTJ or a placebo (PLA) (2 x 250 mL) for 3 days after an initial repeated sprint test (20 x 30 m; RST1) and after a second repeated sprint test (RST2), performed 72 h later. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), reactive strength index (RI), pressure-pain threshold (PPT), creatine kinase (CK), C-reactive protein (hs-CRP), protein carbonyls (PC), lipid hydroperoxides (LOOH) and the ascorbyl free radical (A<sup>•</sup> were measured before, after, and at set times between RST1 and RST2. CMJ and RI recovered quicker in BTJ compared to PLA after RST1: at 72 h post, CMJ and RI were 7.6% and 13.8% higher in BTJ vs. PLA, respectively (p < 0.05). PPT was 10.4% higher in BTJ compared to PLA 24 h post RST2 (p = 0.012) but similar at other time points. No group differences were detected for mean and fastest sprint time or fatigue index. MIVC, or the biochemical markers measured (p > 0.05). BTJ reduced the decrement in CMJ and RI following and RST but had no effect on sprint performance or oxidative stress.
Muscle-shortening velocity and hence power have been shown to increase in the presence of nitric oxide (NO). NO availability increases after consuming nitrate (NO<sub>3</sub><sup>-</sup>). Ingestion of NO<sub>3</sub><sup>-</sup>rich beetroot juice (BRJ) has increased muscle power in untrained adults. PURPOSE: This study determined whether NO<sub>3</sub><sup>-</sup> supplementation could acutely enhance maximal power in trained athletes. METHODS: In this double-blind, crossover study, 13 trained athletes performed maximal inertial-load cycling trials (3-4 s) immediately before (PRE) and after (POST) consuming either NO<sub>3</sub><sup>-</sup>rich (NO3) or NO<sub>3</sub><sup>-</sup>depleted (PLA) BRJ to assess acute changes (ie, within the same day) in maximal power (P<sub>MAX</sub>) and optimal pedaling rate (RPM<sub>OPT</sub>). Participants also performed maximal isokinetic cycling (30 s) to assess performance differences after supplementation. RESULTS: 2 x 2 repeated-measures ANOVA indicated a greater increase in PMAX from PRE to POST NO3 (PRE 1160 ± 301 W to POST 1229 ± 317 W) than with PLA (PRE 1191 ± 298 W to POST 1213 ± 300 W) (P = .009; η<sub>p</sub>² = 0.45). A paired t-test verified a greater relative change in P<sub>MAX</sub> after NO3 (6.0% ± 2.6%) than with PLA (2.0% ± 3.8%) (P = .014; d = 1.21). RPM<sub>OPT</sub> remained unchanged from PRE (123 ± 14 rpm) to POST PLA (122 ± 14 rpm) but increased from PRE (120 ± 14 rpm) to POST NO3 (127 ± 13 rpm) (P = .043; η<sub>p</sub>² = 0.30). There was no relative change in RPM<sub>OPT</sub> after PLA (-0.3% ± 4.1%), but there was an increase after NO3 (6.5% ± 11.4%) (P = .049; d = 0.79). No differences were observed between the 30-s isokinetic trials. CONCLUSIONS: Acute NO<sub>3</sub><sup>-</sup> supplementation can enhance maximal muscle power in trained athletes. These findings may particularly benefit power-sport athletes who perform brief explosive actions.
UNLABELLED: It is possible that dietary nitrate (NO3 (-)) supplementation may improve both physical and cognitive performance via its influence on blood flow and cellular energetics.
PURPOSE: To investigate the effects of dietary NO3 (-) supplementation on exercise performance and cognitive function during a prolonged intermittent sprint test (IST) protocol, which was designed to reflect typical work patterns during team sports.
METHODS: In a double-blind randomised crossover study, 16 male team-sport players received NO3 (-)-rich (BR; 140 mL day(-1); 12.8 mmol of NO3 (-)), and NO3 (-)-depleted (PL; 140 mL day(-1); 0.08 mmol NO3 (-)) beetroot juice for 7 days. On day 7 of supplementation, subjects completed the IST (two 40-min "halves" of repeated 2-min blocks consisting of a 6-s "all-out" sprint, 100-s active recovery and 20 s of rest), on a cycle ergometer during which cognitive tasks were simultaneously performed.
RESULTS: Total work done during the sprints of the IST was greater in BR (123 ± 19 kJ) compared to PL (119 ± 17 kJ; P < 0.05). Reaction time of response to the cognitive tasks in the second half of the IST was improved in BR compared to PL (BR first half: 820 ± 96 vs. second half: 817 ± 86 ms; PL first half: 824 ± 114 vs. second half: 847 ± 118 ms; P < 0.05). There was no difference in response accuracy.
CONCLUSIONS: These findings suggest that dietary NO3 (-) enhances repeated sprint performance and may attenuate the decline in cognitive function (and specifically reaction time) that may occur during prolonged intermittent exercise.
<b>INTRODUCTION: </b>Sodium phosphate (SP) and beetroot juice (BJ) supplementation was assessed on repeated-sprint ability (RSA).<b>METHODS: </b>Thirteen female team-sport participants completed four trials: (1) SP and BJ (SP + BJ), (2) SP and placebo (for BJ), (3) BJ and placebo (for SP) and (4) placebo (for SP + BJ), with ~21 days separating each trial. After each trial, participants performed a simulated team-game circuit (STGC) consisting of four 15 min quarters, with a 6 × 20-m repeated-sprint set performed at the start, half-time and end.<b>RESULTS: </b>Total sprint times were between 0.95-1.30 and 0.83-1.12 s faster for each RSA set and 3.25 and 3.12 s faster overall (~5% improvement) after SP compared with placebo and BJ, respectively (p = 0.02 for sets 1, 2 and overall; Cohen's effect size: d = -0.51 to -0.90 for all sets and overall). Additionally, total sprint times were 0.48 s faster after SP + BJ compared with placebo (set 2; p = 0.05, ~2% improvement). Furthermore, best sprints were 0.13-0.23 and 0.15-0.20 s faster (~6% improvement; p < 0.01) after SP compared with placebo and BJ, respectively, for all sets (d = -0.54 to -0.89).<b>CONCLUSION: </b>SP improved RSA in team-sport, female athletes when fresh (set 1) and during the later sets of a STGC (sets 2 and 3). Specifically, total and best sprint times were faster after SP compared with placebo and BJ.
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.
PURPOSE: Nitrate supplementation improves endurance exercise and single bouts of high-intensity activity, but its effect on repeated sprints is unclear. This study is the first to investigate the effects of acute dietary nitrate supplementation during a high-intensity intermittent-sprint test to exhaustion.
METHODS: Team-sport athletes (9 male, age 22.3 ± 2.1 y, VO2max 57.4 ± 8.5 mL · kg-1 · min-1; 7 female, age 20.7 ± 1.3 y, VO2max 47.2 ± 8.5 mL · kg-1 · min-1) were assigned to a double-blind, randomized, crossover design. Participants consumed 70 mL of concentrated beetroot juice containing a minimum of 0.3 g of nitrate (NT) or 70 mL of placebo (PL) 2 h before a repeated-sprint protocol involving repeated 8-s sprints with 30-s recovery on a cycle ergometer to exhaustion.
RESULTS: Fewer sprints (NT = 13 ± 5 vs PL = 15 ± 6, P = .005, d = 0.41) and less total work (NT = 49.2 ± 24.2 kJ vs PL = 57.8 ± 34.0 kJ, P = .027, d = 0.3) were completed in NT relative to PL. However there was no difference in overall mean power output or the mean power output for each individual 8-s sprint.
CONCLUSIONS: These findings suggest that dietary nitrate is not beneficial for improving repeated-sprint performance, at least when such sprints are near-maximal and frequent in nature. The lack of an effect of nitrate at near-maximal oxygen uptake supports the suggestion that at greater exercise intensities nitrate does not have an ergogenic effect.
The aim of the current study was to determine the effects of dietary nitrate ingestion on parameters of submaximal and supramaximal exercise and time trial (TT) performance in trained kayakers. Eight male kayakers completed four exercise trials consisting of an initial discontinuous graded exercise test to exhaustion and three performance trials using a kayak ergometer. The performance trials were composed of 15 min of paddling at 60% of maximum work rate, five 10-s all-out sprints, and a 1 km TT. The second and third trials were preceded by ingestion of either 70 ml nitrate-rich concentrated beetroot juice (BR) or tomato juice (placebo [PLA]) 3 hr before exercise using a randomized crossover design. Plasma nitrate (PLA: 33.8 ± 1.9 μM, BR: 152 ± 3.5 μM) and nitrite (PLA: 519.8 ± 25.8, BR: 687.9 ± 20 nM) were higher following ingestion of BR compared with PLA (both p < .001). VO2 during steady-state exercise was lower in the BR trial than in the PLA trial (p = .010). There was no difference in either peak power in the sprints (p = .590) or TT performance between conditions (PLA: 277 ± 5 s, BR: 276 ± 5 s, p = .539). Despite a reduction in VO2, BR ingestion appears to have no effect on repeated supramaximal sprint or 1 km TT kayaking performance. A smaller elevation in plasma nitrite following a single dose of nitrate and the individual variability in this response may partly account for these findings.
Recent studies have suggested that dietary inorganic nitrate (NO₃(-)) supplementation may improve muscle efficiency and endurance exercise tolerance but possible effects during team sport-specific intense intermittent exercise have not been examined. We hypothesized that NO₃(-) supplementation would enhance high-intensity intermittent exercise performance. Fourteen male recreational team-sport players were assigned in a double-blind, randomized, crossover design to consume 490 mL of concentrated, nitrate-rich beetroot juice (BR) and nitrate-depleted placebo juice (PL) over ~30 h preceding the completion of a Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1). Resting plasma nitrite concentration ([NO₂(-)]) was ~400% greater in BR compared to PL. Plasma [NO₂(-)] declined by 20% in PL (P < 0.05) and by 54 % in BR (P < 0.05) from pre-exercise to end-exercise. Performance in the Yo-Yo IR1 was 4.2% greater (P < 0.05) with BR (1,704 ± 304 m) compared to PL (1,636 ± 288 m). Blood [lactate] was not different between BR and PL, but the mean blood [glucose] was lower (3.8 ± 0.8 vs. 4.2 ± 1.1 mM, P < 0.05) and the rise in plasma [K(+)] tended to be reduced in BR compared to PL (P = 0.08). These findings suggest that NO₃(-) supplementation may promote NO production via the nitrate-nitrite-NO pathway and enhance Yo-Yo IR1 test performance, perhaps by facilitating greater muscle glucose uptake or by better maintaining muscle excitability. Dietary NO₃(-) supplementation improves performance during intense intermittent exercise and may be a useful ergogenic aid for team sports players.
