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| Name | Class |
|---|---|
| Universidad Complutense de Madrid | OTHER |
| University of Seville | OTHER |
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Beetroot juice is a good source of nitrate (NO3-), which is a precursor of nitric oxide (NO) through the NO3- to nitrite (NO2-) to NO pathway (Lundberg et al., 2008). Consequently, it is thought that a minimum threshold may exist for dietary NO3- consumption of at least 5 mmol to enhance athletic performance (Senefeld et al., 2020). In turn, systematic reviews have documented that the use of beetroot juice supplementation enhances muscle strength and power-related attributes (Gonzalez et al., 2023), as well as performance in repeated high-intensity activity bouts (Alsharif et al., 2023; Dominguez et al., 2018). However, beetroot juice supplementation has been shown to have equivocal effects on neuromuscular performance specifically among individual sport athletes (e.g. taekwondo). Thus, the aim of this study was to determine the effects of acute beetroot juice ingestion (140 mL, 12.8 mmol NO3-) on neuromuscular performance in elite female taekwondo athletes.
Beetroot juice is a good source of nitrate (NO3-), which is a precursor of nitric oxide (NO) through the NO3- to nitrite (NO2-) to NO pathway (Lundberg et al., 2008). This pathway is thought to promote increased sarcoplasmic reticulum calcium release and re-uptake with ensuing enhancements in force output within type II muscle fibers (Hernandez et al., 2012), as well as increased neurotransmitter release (Esen et al., 2022) and attenuated muscle potassium efflux (Wylie et al., 2013) that could benefit neuromuscular performance. Consequently, it is thought that a minimum threshold may exist for dietary NO3- consumption of at least 5 mmol to enhance athletic performance (Senefeld et al., 2020). In turn, systematic reviews have documented that the use of beetroot juice supplementation enhances muscle strength and power-related attributes (Gonzalez et al., 2023), as well as performance in repeated high-intensity activity bouts (Alsharif et al., 2023; Dominguez et al., 2018). However, beetroot juice supplementation has been shown to have equivocal effects on neuromuscular performance specifically among individual sport athletes (e.g. taekwondo). Thus, the aim of this study was to determine the effects of acute beetroot juice ingestion (140 mL, 12.8 mmol NO3-) on neuromuscular performance in elite female taekwondo athletes.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Beetroot juice supplementation | Experimental | 140 mL of beetroot juice (12.8 mmol of NO3-, Beet-It-Pro Elite Shot, James White Drinks Ltd., Ipswich, UK) made from concentrates of beetroot juice (98%) and lemon juice (2%) (nutritional information (per 100 mL), energy: 373 kJ; fat: 0 g; carbohydrates: 18 g [sugars: 17 g]; protein: 3.7 g; salt: 0.48 g) |
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| Placebo supplementation | Placebo Comparator | 140 mL of beetroot juice placebo without nitrates (0.08 mmol of NO3-, Beet-It-Pro Elite Shot, James White Drinks Ltd., Ipswich, UK) made from concentrates of beetroot juice (98%) and lemon juice (2%) (nutritional information (per 100 mL), energy: 373 kJ; fat: 0 g; carbohydrates: 18 g [sugars: 17 g]; protein: 3.7 g; salt: 0.48 g) |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Beetroot juice (James White, UK) | Dietary Supplement | One serving 140 mL of BJ (12.8 mmol of NO3-; Beet-It-Pro Elite Shot, James White Drinks Ltd., Ipswich, UK) after an overnight fast and 2.5 h before initiating the testing session. |
| Measure | Description | Time Frame |
|---|---|---|
| Simulated taekwondo Combat (actions/time) | Simulated taekwondo combat were performed according to the guidelines of the World Taekwondo (WT), and participants were divided based in the Olympic weight categories (WT, 2016). All the combats were executed in an official octagonal and homologated competition area while an international referee (who doesn´t know the experimental treatments) arbitrated. Today the rules of WTF led to use electronic protectors as protecting of athletes and identify electronically the punctuations (Del Vecchio, Franchini, Del Vecchio, & Pieter, 2011). Variables analyzed were attack time (AT), step time (ST), pause time (PT), period without attack (PWA = ST+PT), numbers of attacks (AN), the ratio for attack time and step time (R1 = AT/ST), and ratio for action time and step time (R2 = (AT+ST) /PT). | 1-week |
| Measure | Description | Time Frame |
|---|---|---|
| Changes in maximal jump height (cm) | Maximal jump height using a contact platform | 1-week |
| Reaction time (ms) | Reaction times in a specific reaction test with BlazePod ((Play Coyotta Ltd., Tel Aviv, Israel) |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Universida Pontificia Comillas | Madrid | Spain |
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| Placebo acute supplementation (James White, UK) | Dietary Supplement | One serving 140 mL of BJ (0.04 mmol of NO3-; Beet-It-Pro Elite Shot, James White Drinks Ltd., Ipswich, UK) after an overnight fast and 2.5 h before initiating the testing session. |
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| 1-week |
| Blood lactate concentrations (mmol·L-1) | Previous to the warm-up, just to the end of the simulated combat, and 3 minutes after, a researcher extracted a blood sample of the pad of the index finger of the left hand of the participants. | 1-week |
| Rating of percevied exertion (RPE) (measured using scale 6-20 points) | Immediately after each one of the 3 assaults, participants were asked for providing her RPE using a Borg scale from 6 to 20 points | 1-week |