An interventional study of Nitrate-Rich Beetroot Juice and Nitrate-Depleted Beetroot Juice (Placebo) in Beetroot Juice and Placebo, sponsored by Universidad Pontificia Comillas. Active, not recruiting at 1 site in Spain. Open to male participants aged 18 Years to 35 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by Universidad Pontificia Comillas · Not applicable, Interventional, and Treatment
Beetroot juice is rich in dietary nitrate, a compound that may improve muscle function and exercise performance. However, the effects of different nitrate doses on upper-body strength and muscular endurance are lees explored. In this randomized, double-blind, placebo-controlled crossover study, participants will complete four experimental conditions involving different doses of beetroot juice (0, 6.4, 12.8, and 19.2 mmol of nitrate from active supplementation) in a randomized order. Each condition will consist of three 70-mL shots (210 mL in total), containing different combinations of nitrate-rich beetroot juice and placebo. Neuromuscular performance will be assessed through bench press exercises at different intensities, evaluating bar movement velocity and muscular endurance. Salivary nitrate and nitrite concentrations, perceived exertion, and potential side effects will also be assessed. The study aims to determine whether increasing doses of beetroot juice produce different effects on neuromuscular performance.
The study follows a randomized, double-blind, placebo-controlled crossover design. Each participant will complete four experimental supplementation conditions in a randomized order. The conditions will involve the ingestion of three 70-mL shots (210 mL in total), containing different combinations of nitrate-rich beetroot juice and placebo: three placebo shots, one beetroot juice shot and two placebo shots, two beetroot juice shots and one placebo shot, or three beetroot juice shots. Each active beetroot juice shot will provide approximately 6.4 mmol of nitrate.
Neuromuscular performance will be assessed using the bench press exercise at four relative intensities: 25%, 50%, 75%, and 90% of one-repetition maximum (1RM). Participants will perform three repetitions at 25% 1RM, two repetitions at 50% 1RM, two repetitions at 75% 1RM, and one repetition at 90% 1RM. Mean propulsive velocity (m/s) will be evaluated at each intensity. Muscular endurance will also be assessed through a bench press test performed at 65% 1RM, during which participants will complete the maximum possible number of repetitions until muscular failure.
Additional assessments will include salivary nitrate and nitrite concentrations (µmol/L), potential side effects associated with beetroot juice supplementation using a nine-item questionnaire with yes/no responses, and ratings of perceived exertion using a 1-10 scale.
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Participants will ingest three 70-mL shots of nitrate-depleted beetroot juice (placebo), providing a total volume of 210 mL, before performing the bench press testing protocol.
Dietary Supplement: Nitrate-Depleted Beetroot Juice (Placebo)
Participants will ingest one 70-mL shot of nitrate-rich beetroot juice (6.4 mmol of nitrate) and two 70-mL placebo shots, providing a total volume of 210 mL, before performing the bench press testing protocol.
Dietary Supplement: Nitrate-Rich Beetroot Juice
Participants will ingest two 70-mL shots of nitrate-rich beetroot juice (12.8 mmol of nitrate) and one 70-mL placebo shot, providing a total volume of 210 mL, before performing the bench press testing protocol.
Dietary Supplement: Nitrate-Rich Beetroot Juice
Participants will ingest three 70-mL shots of nitrate-rich beetroot juice (19.2 mmol of nitrate), providing a total volume of 210 mL, before performing the bench press testing protocol.
Dietary Supplement: Nitrate-Rich Beetroot Juice
Nitrate-rich beetroot juice supplementation administered orally in 70-mL shots, each containing approximately 6.4 mmol of nitrate (NO3-). Participants will receive one, two, or three active shots, corresponding to 6.4, 12.8, or 19.2 mmol of nitrate from active supplementation, respectively. The total volume administered in each experimental condition will be 210 mL, using placebo shots when necessary.
Nitrate-depleted beetroot juice administered orally in 70-mL shots as a placebo. Participants will receive one, two, or three placebo shots depending on the experimental condition, maintaining a total supplementation volume of 210 mL. The placebo will be used as the control condition and in combination with active beetroot juice to maintain the double-blind design.
Mean Propulsive Velocity During Bench Press at 25% 1RM
Mean propulsive velocity (m/s) will be assessed during three repetitions of the bench press exercise performed at 25% of the participant's one-repetition maximum (1RM).
Time frame: During the bench press assessment following supplementation in each of the four experimental sessions.
Mean Propulsive Velocity During Bench Press at 50% 1RM
Mean propulsive velocity (m/s) will be assessed during two repetitions of the bench press exercise performed at 50% of the participant's one-repetition maximum (1RM).
Time frame: During the bench press assessment following supplementation in each of the four experimental sessions.
Mean Propulsive Velocity During Bench Press at 75% 1RM
Mean propulsive velocity (m/s) will be assessed during two repetitions of the bench press exercise performed at 75% of the participant's one-repetition maximum (1RM).
Time frame: During the bench press assessment following supplementation in each of the four experimental sessions.
Mean Propulsive Velocity During Bench Press at 90% 1RM
Mean propulsive velocity (m/s) will be assessed during one repetition of the bench press exercise performed at 90% of the participant's one-repetition maximum (1RM).
Time frame: During the bench press assessment following supplementation in each of the four experimental sessions.
Maximum Number of Bench Press Repetitions to Failure at 65% 1RM
Muscular endurance will be assessed by recording the maximum number of complete repetitions performed during the bench press exercise at 65% of the participant's one-repetition maximum (1RM) until muscular failure.
Time frame: During the 65% 1RM repetitions-to-failure test in each of the four experimental sessions.
Salivary Nitrate and Nitrite Concentrations
Salivary nitrite concentration (µmol/L) will be measured to assess changes in nitric oxide-related metabolism (i.e., nitrate and nitrites) following different doses of nitrate-rich beetroot juice supplementation. Saliva samples will be collected 2.5 hours after supplement ingestion, immediately before the start of the exercise protocol, during each of the four experimental sessions
Time frame: 2.5 hours after supplement ingestion, immediately before exercise, during each of the four experimental sessions.
Salivary Nitrite Concentration
Salivary nitrite concentration (µmol/L) will be measured to assess changes in nitric oxide-related metabolism following different doses of nitrate-rich beetroot juice supplementation.
Time frame: At the protocol-specified saliva collection time points during each of the four experimental sessions.
Side Effects Related to Beetroot Juice Supplementation
Potential side effects associated with beetroot juice ingestion will be assessed using a questionnaire consisting of nine items, each answered with "Yes" or "No", to identify the occurrence of supplementation-related symptoms.
Time frame: 24 hours after supplement ingestion, during each of the four experimental sessions.
Rating of Perceived Exertion During Bench Press Exercise
Perceived exertion will be assessed using a rating of perceived exertion (RPE) scale ranging from 1 to 10 points, with higher scores indicating greater perceived effort during the bench press exercise.
Time frame: 30 minutes after completion of the exercise protocol, during each of the four experimental sessions.
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Universidad Pontificia Comillas