The Effects of Acute Nitrate and Caffeine Co-ingestion on Discipline-Specific Exercise Performance.

NCT07748416 | Not Yet Recruiting

• 1 other identifier: ZDS2026_NG_001
• Study Type: interventional
• Target: 112
• Locations: 1 country
• Sites: 1

Brief Summary

The purpose of this study is to investigate the acute, separate, and combined ergogenic effects of dietary nitrate (beetroot juice, BJ) and caffeine (CAF) supplementation on discipline-specific athletic performance. The project employs a double-blind, randomized, placebo-controlled, four-arm crossover design. It evaluates two highly distinct, heterogeneous populations of athletes: (A) adult high-intensity functional training (HIFT/CrossFit/Hyrox) competitors performing the standardized Hyrox Physical Fitness Test (P'F'T), and (B) elite junior competitive swimmers (National Team members) performing a progressive 8 × 100 m swimming test. The study will assess physical performance, lactate kinetics, subjective exertion, biochemical indices, psychological metrics, and gastrointestinal tolerance.

Conditions

Athletic Performance; Dietary Supplement; Iron Status

Keywords

Caffeine; Sports nutrition; Swimming; High-Intensity Functional Training; Nitric oxide

Outcome Measures

Primary Outcomes (2)

• Exercise Performance Time (minutes and seconds, Cohort A - Hyrox P'F'T)

  Total time (in minutes and seconds) required to complete the standardized HYROX Physical Fitness Test (P'F'T) consisting of 6 specific functional exercises.

  At each experimental visit (Visits T1-T4), with visits conducted at 7-day intervals following the baseline/familiarization visit (T0).

• Swimming Performance (minutes and seconds, Cohort B - 8x100m Step-Test)

  Swimming performance will be assessed using the completion time (seconds and milliseconds) for each 100-m repetition of the standardized 8 × 100-m step test, including the maximal-effort repetition performed during the fifth stage.

  At each experimental visit (Visits T1-T4), with visits conducted at 7-day intervals following the baseline/familiarization visit (T0).

Secondary Outcomes (31)

• Blood Lactate Kinetics (mmol/L)

  Before supplementation (baseline), pre-exercise (3 hours after beetroot juice supplementation and 30 minutes after caffeine supplementation), and 3 and 7 minutes after exercise at each experimental visit (Visits T1-T4; 7-day intervals).

• Heart Rate (HR, bpm)

  Continuously monitored during exercise at each experimental visit (Visits T1-T4; 7-day intervals).

• Rating of Perceived Exertion (RPE, points)

  Immediately after exercise at each experimental visit (Visits T1-T4; 7-day intervals).

• Blood Pressure (mmHg)

  Measured 2.5 hours after beetroot juice supplementation and 30 minutes after caffeine supplementation (pre-exercise) at each experimental visit (Visits T1-T4; 7-day intervals).

• Gastrointestinal Tolerance Profile (mVAS, points)

  Measured 30 minutes after supplementation and immediately after exercise at each experimental visit (Visits T1-T4; 7-day intervals).

Study Arms (4)

CAF + BJ (Active Co-ingestion)

EXPERIMENTAL

Participants ingest a concentrated beetroot juice shot (\~6.4 mmol / 400 mg nitrates) 3 hours before exercise, and a capsule of caffeine (Cohort A: 6 mg/kg body mass; Cohort B: 3 mg/kg body mass) 60 minutes before exercise.

Dietary Supplement: Caffeine; Dietary Supplement: Dietary Nitrate (Beetroot Juice)

CAF + PLBJ (Caffeine + Placebo BJ)

ACTIVE COMPARATOR

Participants ingest a nitrate-depleted beetroot juice shot (\~0.04 mmol nitrates) 3 hours before exercise, and a capsule of caffeine (Cohort A: 6 mg/kg body mass; Cohort B: 3 mg/kg body mass) 60 minutes before exercise.

Dietary Supplement: Caffeine; Dietary Supplement: Placebo (Nitrate-Depleted Beetroot Juice)

PLCAF + BJ (Placebo CAF + Beetroot Juice)

ACTIVE COMPARATOR

Participants ingest a concentrated beetroot juice shot (\~6.4 mmol / 400 mg nitrates) 3 hours before exercise, and a placebo capsule (maltodextrin) 60 minutes before exercise.

Dietary Supplement: Dietary Nitrate (Beetroot Juice); Dietary Supplement: Placebo (Maltodextrin Capsule)

PLCAF + PLBJ (Double Placebo Control)

PLACEBO COMPARATOR

Participants ingest a nitrate-depleted beetroot juice shot (\~0.04 mmol nitrates) 3 hours before exercise, and a placebo capsule (maltodextrin) 60 minutes before exercise.

Dietary Supplement: Placebo (Maltodextrin Capsule); Dietary Supplement: Placebo (Nitrate-Depleted Beetroot Juice)

Interventions

Caffeine DIETARY_SUPPLEMENT

Anhydrous caffeine administered orally in a hard gelatine capsule. To address the unique physiological profiles of the two cohorts, a highly specific, differentiated dosing protocol is implemented: Cohort A (adult functional fitness athletes) will receive a high-performance dose of 6 mg/kg body mass, while Cohort B (elite junior swimmers) will receive a safe, youth-adapted dose of 3 mg/kg body mass. In all experimental trials, the capsule is ingested exactly 60 minutes prior to the onset of the discipline-specific exercise test to match peak plasma caffeine concentration.

CAF + BJ (Active Co-ingestion); CAF + PLBJ (Caffeine + Placebo BJ)

Dietary Nitrate (Beetroot Juice) DIETARY_SUPPLEMENT

Concentrated beetroot juice (BJ) administered as a single, acute organic shot of 70 mL (Beet It Sport, James White Drinks Ltd., Ipswich, UK). Each active shot contains approximately 400 mg (equivalent to \~6.4 mmol) of inorganic nitrate. In contrast to chronic loading designs, this study evaluates purely acute effects; the shot is ingested exactly 3 hours (180 minutes) prior to the physical performance test to align with peak systemic concentration of plasma nitrite.

CAF + BJ (Active Co-ingestion); PLCAF + BJ (Placebo CAF + Beetroot Juice)

Placebo (Maltodextrin Capsule) DIETARY_SUPPLEMENT

Placebo capsule containing inert maltodextrin powder. The capsule is identical in size, shape, weight, color (opaque), and texture to the active caffeine capsule to ensure robust blinding. It is administered at the exact same time point (60 minutes pre-exercise) according to the identical body-mass-adjusted dosing scheme (simulating either 3 mg/kg or 6 mg/kg).

PLCAF + BJ (Placebo CAF + Beetroot Juice); PLCAF + PLBJ (Double Placebo Control)

Placebo (Nitrate-Depleted Beetroot Juice) DIETARY_SUPPLEMENT

Nitrate-depleted beetroot juice (Beet It, James White Drinks Ltd., Ipswich, UK) administered as a 70 mL shot. This placebo is identical in taste, smell, appearance, packaging, and viscosity to the active concentrated shot, but has been selectively filtered to contain negligible nitrate levels (\<0.4 mmol / \~25 mg of nitrates). It is ingested exactly 3 hours prior to the exercise test.

CAF + PLBJ (Caffeine + Placebo BJ); PLCAF + PLBJ (Double Placebo Control)

Eligibility Criteria

• Age: 16 Years - 45 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• A) Cohort A (HIFT / CrossFit / Hyrox):
• Aged 18-45 years.
• Minimum of 2 years of systematic HIFT/CrossFit/Hyrox training experience.
• Performing \>4 training sessions per week.
• Ability to perform the HYROX Physical Fitness Test (P'F'T) and has participated in at least one official HYROX event.
• Possession of a valid medical certificate proving eligibility for competitive sports.
• B) Cohort B (Competitive Junior Swimmers):
• Aged 16-19 years.
• Active member of the Polish Junior National Swimming Team.
• Minimum of 5 years of competitive swimming experience.
• Current training volume of at least 8-10 pool training sessions per week.
• Written informed consent obtained from both the participant and their legal guardian (for minors under 18).
• C)Common Criteria for Both Cohorts:
• No history of cardiovascular, respiratory, metabolic, or musculoskeletal disease contradicting high-intensity exercise or stimulant intake.
• No known food allergies or adverse reactions to beetroot products or caffeine.

You may not qualify if:

• Occurrence of acute musculoskeletal injury or trauma during the study period.
• Any medical or health contraindications (including severe menstrual disorders, planned pregnancy, or breastfeeding).
• Failure or refusal to strictly adhere to the dietary, supplementation, and exercise testing protocols.

Sponsors & Collaborators

• Poznan University of Physical Education: lead

Study Sites (1)

Poznan University of Physical Education

Poznan, Wielkopolska, 61-871, Poland

Location

MeSH Terms

Interventions

Caffeine; maltodextrin

Intervention Hierarchy (Ancestors)

Xanthines; Alkaloids; Heterocyclic Compounds; Purinones; Purines; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring

Study Officials

• Natalia Główka, PhD

  Poznan University of Physical Education, Department of Sports Dietetics

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Natalia Główka, PhD

CONTACT

+48691756944; glowka@awf.poznan.pl

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: This study employs a double-blind, randomized, placebo-controlled, four-arm, crossover design to evaluate the acute, separate, and combined effects of caffeine (CAF) and dietary nitrate (beetroot juice, BJ) on athletic performance. Following a baseline familiarization session (T0), participants will complete four main experimental testing visits (T1-T4). Every participant will undergo all four interventional conditions in a randomized, counterbalanced sequence. A minimum 7-day (168-hour) washout period will separate each testing session to ensure complete physical recovery, muscle regeneration, and complete elimination of the active substances from the systemic circulation. The four interventional combinations administered across the testing visits are: Active BJ + Active CAF (CAF+BJ); Active CAF + BJ (CAF+PLBJ); Active BJ + Placebo CAF (PLCAF+BJ); Placebo BJ + Placebo CAF (PLCAF+PLBJ).

Study Record Dates

• First Submitted: July 17, 2026
• First Posted: August 5, 2026
• Study Start (Estimated): October 1, 2026
• Primary Completion (Estimated): June 30, 2029
• Study Completion (Estimated): June 30, 2029
• Last Updated: August 7, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL
• Time Frame: The study protocol will be available upon its publication. The IPD and analytic code will be available starting from the date of the primary study results publication and will remain accessible for at least 5 years.
• Access Criteria: The study protocol will be published as an open-access article. Upon completion of the study, de-identified individual participant data (IPD) and relevant analytic code will be deposited in an open-access repository such as Zenodo or OSF, in accordance with FAIR principles.

Locations

PL (1)