Background
Methodology
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Studies performed in non-adults (samples including subjects aged <18 or >65 years).
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Studies conducted in vitro or in animals.
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Studies in which the direct effects of BJ were not determined.
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Studies in which impacts were examined on exercises that did not comply with the characteristics of intermittent, high-intensity efforts.
Results
Study selection
Study characteristics
Study results
Reference | Subjects | Study design | Dose | Exercise test | Results |
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Muggeridge et al. [38] | Trained kayakers (male, n = 8) (VO2peak 49.0 ± 6.1 ml·kg·min−1) | Single-blind, randomized, cross-over | 5 mmol NO3− (180 min before) | Kayak ergometer: 5 × 10 s sprint-rest 50 s | +4% average power (420 ± 23 vs 404 ± 24 W) |
Martin et al. [53] | Recreation team sport players (male,n = 16) (VO2peak 47.2 ± 8.5 ml·kg·min−1) | Double-blind, randomized, cross-over | 6.4 mmol NO3− (120 min before) | Cycle ergometer: sets until exhaustion of 8 s– rest 30 s | −13% reps (13 ± 5 vs 15 ± 6) and −17% total work (49.2 ± 24.2 vs 57.8 ± 34.0 kJ) |
Aucouturier et al. [54] | Recreation team sport players (male, n = 12) (VO2peak 46.6 ± 3.4 ml·kg·min−1) | Single-blind, randomized, cross-over | 10.9 mmol NO3− (180 min before) | Cycle ergometer: sets until exhaustion of 15 s at 170% MAP–rest 30 s | +20% reps* (26.1 ± 10.7 vs 21.8 ± 8.0) and 18% total workload* (168.2 ± 60.2 vs 142.0 ± 46.8 kJ) |
Buck et al. [55] | Amateur team sport players (female, n = 13) (VO2peak not specified) | Double-blind, randomized, Latin-square | BJ: 6.4 mmol NO3− (6 days) BJ + SP: 6.4 mmol NO3− + 50 mg·kg lean mass SP (6 days) | PRE, MID and POST simulation team sport matches: 6×(20 m sprint + rest 25 s) | BJ: −0.2% total sprint time per set (69.8 ± 4.9 vs 69.97 ± 4.2) BJ + SP: −2% total sprint time per set (68.9 ± 5.1 vs 69.97 ± 4.2) |
Thompson et al. [56] | Recreation team sport players (male, n = 16) (VO2peak 50 ± 7 ml·kg·min−1) | Double-blind, randomized, cross-over | 12.8 mmol NO3− (7 days) | MID and POST simulated team-sport matches: 2×[5×(6 s cycle ergometry sprint + rest 14 s)] | 5% work volume at MID* (63 ± 20 vs 60 ± 18 kJ), 2% POST (60 ± 17 vs 59 ± 16 kJ) and 4% whole session* (123 ± 19 vs 119 ± 17 kJ) |
Clifford et al. [57] | Competition team sport players (male, n = 20) (VO2peak not specified) | Double-blind, independent groups design | 11.4 mmol NO3− (150 min before) | 2xRST: 20×(30 m sprint–rest 30 s) | -1% average sprint time RST1 (4.65 ± 0.3 vs 4.7 ± 0.2 s) and −2% RST2 (4.66 ± 0.2 vs 4.77 ± 0.2 s) and −2% fastest sprint RST1 (4.41 ± 0.2 vs 4.48 ± 0.1 s) and −3%RST2 (4.38 ± 0.2 vs 4.53 ± 0.2 s) |
Mosher et al. [58] | Recreation sport players (male, n = 12) (VO2peak not specified) | Double-blind, randomized, cross-over | 6.4 mmol NO3− (6 days) | Bench press: 3×(maximum number reps at 60% 1 RM) | + 19% weight lifted in session and improved no. of reps S1*, S2*, S3* and whole session. *improvements not specified |
Rimer et al. [59] | Competition sport players (male, n = 13) (VO2peak not specified) | Double-blind, randomized, cross-over | 11.2 mmol NO3− (150 min before) | Isokinetic cycle ergometer: Wingate 30-s test | -1% peak power (1173 ± 255 vs 1185 ± 249 W) and −1% total work (22.8 ± 4.8 vs 23 ± 4.8 W) |
Wylie et al. [60] | Recreation team sport players (male, n = 10) (VO2peak 58 ± 8 ml·kg·min−1) | Double-blind, randomized, cross-over design | 8.4 mmol NO3− (5 days) | Cycle ergometer: 24 x (6 s sprint–rest 24 s) Cycle ergometer: 7 x (30 s sprint–rest 4 min) Cycle ergometer: 6 x (60 s sprint–rest 60 s) | +5% mean average power* (568 ± 136 vs 539 ± 136 W) and +1% mean peak power (792 ± 159 vs 782 ± 154 W) in 24 x (6 s sprint–rest 24 s);−1% mean average power (558 ± 95 vs 562 ± 94 W) and −1% mean peak power (768 ± 157 vs 776 ± 142 W) in 7 x (30 s sprint–rest 4 min) |
Discussion
Effects of chronic supplementation with beetroot juice on intermittent, high-intensity exercise efforts
Effects of chronic supplementation with beetroot juice on resistance training
Effects of chronic supplementation with beetroot juice on intermittent high-intensity exercise efforts
Effects of acute beetroot juice supplementation on intermittent high-intensity efforts
Conclusions
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Supplementation with beetroot juice has been shown to diminish the muscular fatigue associated with high-intensity exercise efforts, though it is not known if this is achieved by reducing fatigue and muscle damage and/or promoting muscle regeneration postexercise.
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When faced with exercise efforts that could considerably deplete phosphocreatine reserves (sets of resistance training or repetitive sprints of around 15 s interspersed with short rest periods) and given that phosphocreatine resynthesis requires an oxidative metabolism, beetroot juice could help the recovery of phosphocreatine reserves and thus avoid its depletion during repeated efforts. In parallel, supplementation would limit the build-up of metabolites such as ADP and inorganic phosphates, which are known to induce muscular fatigue.
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Beetroot juice has been shown to improve the release and reuptake of calcium at the sarcoplasmic reticulum. This could help the power production associated with improvements in muscle shortening velocity. Non-isokinetic ergometers (in which movement velocity is not assessed) are sensitive to such improvements in power generation.
Study limitations
Future lines of research
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As it has been proposed that beetroot juice supplementation improves phosphocreatine resynthesis during the brief rest periods included in protocols of intermittent high-intensity exercise, future studies are needed to confirm via a muscle biopsy phosphocreatine levels during repeated high-intensity efforts.
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To examine the possible beneficial effect of beetroot juice on muscle shortening velocity reflected as improved pedalling cadence, future studies need to assess the ergogenic effect of this supplement in a single, constant-load test on an inertial cycle ergometer.
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To elucidate the mechanism whereby beetroot juice diminishes muscular fatigue and improves recovery from this fatigue, the effects of ingesting NO3− on biomarkers of inflammation and muscle damage need to be addressed.
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According to the results of the study in which an ergolytic effect was produced in response to a single dose of beetroot juice administered 120 min before exercise, future investigations should determine the most appropriate timing of supplementation to optimize its ergogenic potential.
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Finally, owing to the possible beneficial impacts of beetroot juice, we will need to assess the interactions of beetroot juice with other supplements of proven ergogenic effects in this type of exercise effort such as caffeine, creatine, β-alanine and sodium bicarbonate.