Effect of the Combination of Nitrate and Caffeine on Critical Power In Trained Male Cyclists

NCT07501806 | Completed

• 1 other identifier: IRB-20-170
• Study Type: interventional
• Target: 15
• Locations: 1 country
• Sites: 1

Brief Summary

This study is investigating the independent and combined effects of acute dietary nitrate and caffeine supplementation on performance during a 3-minute all-out cycling test in trained male cyclists. In a randomized, double-blind, placebo-controlled, crossover design, participants will complete four experimental conditions: nitrate, caffeine, nitrate plus caffeine, and placebo. Primary outcomes include end power (EP) and work done above end power (WEP), surrogate measures of critical power and W'. The study aims to determine whether combined supplementation provides additive benefits for severe-intensity exercise performance.

Conditions

Exercise Performance of Fit Athletes; Exercise Performance; Cycling Performance

Keywords

dietary nitrate; caffeine; beetroot juice; critical power,; cycling; exercise physiology; ergogenic aids

Outcome Measures

Primary Outcomes (2)

• End Power

  End power (EP) will be determined as the average power output over the final 30 seconds of the 3-minute all-out cycling test and will be used as a surrogate measure of critical power.

  Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation

• Work Above End Power

  Work performed above end power (WEP) will be calculated as the total work completed above EP during the 3-minute all-out cycling test and will be used as a surrogate measure of W' (anaerobic work capacity).

  Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation

Secondary Outcomes (2)

• Peak Power Output

  Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation

• Mean Power Output

  Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation

Study Arms (4)

Nitrate + Caffeine (BR + CAF)

EXPERIMENTAL

Participants consume nitrate-rich beetroot juice 3 hours prior to exercise and caffeine 60 minutes prior to exercise.

Dietary Supplement: Dietary Nitrate; Dietary Supplement: Caffeine

Nitrate Only (BR)

EXPERIMENTAL

Participants consume nitrate-rich beetroot juice 3 hours prior to exercise and placebo capsule 60 minutes prior to exercise.

Dietary Supplement: Dietary Nitrate; Other: Placebo

Caffeine Only (CAF)

EXPERIMENTAL

Participants consume nitrate-depleted placebo 3 hours prior to exercise and caffeine 60 minutes prior to exercise.

Dietary Supplement: Caffeine; Other: Placebo

Placebo (PLA)

PLACEBO COMPARATOR

Participants consume nitrate-depleted placebo 3 hours prior to exercise and placebo 60 minutes prior to exercise

Other: Placebo

Interventions

Dietary Nitrate DIETARY_SUPPLEMENT

Participants consume concentrated nitrate-rich beetroot juice providing approximately 8.2 mmol of nitrate 3 hours prior to exercise.

Nitrate + Caffeine (BR + CAF); Nitrate Only (BR)

Caffeine DIETARY_SUPPLEMENT

Participants consume caffeine at a dose of 5 mg/kg body mass in capsule form 60 minutes prior to exercise.

Caffeine Only (CAF); Nitrate + Caffeine (BR + CAF)

Placebo OTHER

Participants consume a nitrate-depleted beetroot juice placebo approximately 2-3 hours prior to exercise and a placebo capsule (maltodextrin) approximately 60 minutes prior to exercise.

Caffeine Only (CAF); Nitrate Only (BR); Placebo (PLA)

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Males between the ages of 18 and 40 years of age
• All participants must be trained cyclists, having participated in structured cycling training consisting of at least 2-3 sessions per week for at least 30-60 min each session during the past 12 months.
• All participants must possess a relative max power output (Wmax) of 4.0 W/kg or greater OR a maximal oxygen consumption (VO2max) of 50 ml/kg/min.
• All participants must be healthy and free of any disease as determined through the completion of a medical history questionnaire.
• Body mass index (BMI) between 18.5 - 30 kg/m\^2 OR bodyfat percentage \<30%

You may not qualify if:

• All females
• Males who are younger than 18 years and older than 40 years of age
• Individuals who have a VO2max below 50 ml/kg/min and a relative Wmax below 4.0 W/kg
• Individuals who fail to meet the minimum training requirements of 2-3 sessions per week of structured cycling training for at least 30-60 min per session during the past 12 months.
• Any individual currently diagnosed with or being treated for any cardiovascular, renal, pulmonary, orthopedic, immunological, psychological or musculoskeletal disorder.
• Any individual who is currently supplementing with a known or purported ergogenic aid (nitrates, caffeine, beta-alanine, bicarbonate, creative, Cordyceps) will be required to refrain from their use for 30 days before beginning the study.
• Individuals who regularly smoke or have quit smoking within the last 6 months.

Sponsors & Collaborators

• Lindenwood University: lead

Study Sites (1)

Exercise and Performance Nutrition Laboratory

Saint Charles, Missouri, 63301, United States

Location

MeSH Terms

Interventions

Caffeine

Intervention Hierarchy (Ancestors)

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

Study Design

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

Model Details: This study uses a randomized, double-blind, placebo-controlled, crossover design in which each participant completes four experimental conditions: nitrate supplementation (BR), caffeine supplementation (CAF), combined nitrate and caffeine supplementation (BR + CAF), and placebo (PLA). The order of conditions is randomized for each participant, and all participants complete all conditions with a washout period of at least 72 hours between trials.

Study Record Dates

• First Submitted: March 19, 2026
• First Posted: March 30, 2026
• Study Start: November 17, 2020
• Primary Completion: November 11, 2021
• Study Completion: November 11, 2021
• Last Updated: March 30, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)