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

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.

Study Overview

• Status: Completed
• Conditions: Exercise Performance; Exercise Performance of Fit Athletes; Cycling Performance
• Intervention / Treatment: Dietary supplement: Dietary Nitrate; Dietary supplement: Caffeine; Other: Placebo

Detailed Description

Dietary nitrate and caffeine are among the most commonly used ergogenic aids in endurance and high-intensity exercise. Nitrate supplementation has been shown to improve exercise efficiency and tolerance to severe-intensity work, potentially through enhanced nitric oxide availability and improved oxygen delivery and utilization. Caffeine, primarily acting through central nervous system stimulation, has been associated with reduced perceived exertion and enhanced performance across a range of exercise modalities. Despite substantial evidence supporting their independent effects, limited research has examined the combined impact of nitrate and caffeine supplementation on exercise performance.

The present study aims to investigate both the independent and combined effects of acute dietary nitrate and caffeine supplementation on performance outcomes derived from a 3-minute all-out cycling test (3MT), a validated method for estimating critical power and W'. Trained male cyclists will complete four experimental trials in a randomized, double-blind, placebo-controlled, crossover design. Experimental conditions include nitrate-rich beetroot juice with caffeine (BR + CAF), nitrate-rich beetroot juice with placebo (BR), nitrate-depleted beetroot juice with caffeine (CAF), and nitrate-depleted beetroot juice with placebo (PLA).

Participants will consume dietary nitrate 3 hours prior to exercise and caffeine (5 mg/kg body mass) 60 minutes prior to testing. Following a standardized protocol, participants will perform a 3-minute all-out cycling test on an electronically braked cycle ergometer. Primary outcome measures include end power (EP) and work performed above end power (WEP), with secondary outcomes including peak power, mean power, and time-specific power output.

This study aims to determine whether co-ingestion of nitrate and caffeine produces additive or synergistic effects on severe-intensity exercise performance, and to evaluate the extent to which these commonly used ergogenic aids influence performance outcomes associated with critical power in trained individuals.

• Study Type: Interventional
• Enrollment (Actual): 15
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Missouri
    • Saint Charles, Missouri, United States, 63301
      • Exercise and Performance Nutrition Laboratory

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• 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%

Exclusion Criteria:

• 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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Nitrate + Caffeine (BR + CAF); Participants consume nitrate-rich beetroot juice 3 hours prior to exercise and caffeine 60 minutes prior to exercise.	Dietary supplement: Dietary Nitrate; Participants consume concentrated nitrate-rich beetroot juice providing approximately 8.2 mmol of nitrate 3 hours prior to exercise.; Dietary supplement: Caffeine; Participants consume caffeine at a dose of 5 mg/kg body mass in capsule form 60 minutes prior to exercise.
Experimental: Nitrate Only (BR); Participants consume nitrate-rich beetroot juice 3 hours prior to exercise and placebo capsule 60 minutes prior to exercise.	Dietary supplement: Dietary Nitrate; Participants consume concentrated nitrate-rich beetroot juice providing approximately 8.2 mmol of nitrate 3 hours prior to exercise.; Other: Placebo; 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.
Experimental: Caffeine Only (CAF); Participants consume nitrate-depleted placebo 3 hours prior to exercise and caffeine 60 minutes prior to exercise.	Dietary supplement: Caffeine; Participants consume caffeine at a dose of 5 mg/kg body mass in capsule form 60 minutes prior to exercise.; Other: Placebo; 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.
Placebo Comparator: Placebo (PLA); Participants consume nitrate-depleted placebo 3 hours prior to exercise and placebo 60 minutes prior to exercise	Other: Placebo; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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 Outcome Measures

Outcome Measure	Measure Description	Time Frame
Peak Power Output	Peak power output will be defined as the highest instantaneous power output achieved during the 3-minute all-out cycling test.	Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation
Mean Power Output	Mean power output will be calculated as the average power output across the entire 3-min all-out cycling test.	Assessed during a single 3-minute all-out cycling test, approximately 3 hours following supplementation

Collaborators and Investigators

• Sponsor: Lindenwood University

Study record dates

Study Major Dates

• Study Start (Actual): November 17, 2020
• Primary Completion (Actual): November 11, 2021
• Study Completion (Actual): November 11, 2021

Study Registration Dates

• First Submitted: March 19, 2026
• First Submitted That Met QC Criteria: March 24, 2026
• First Posted (Actual): March 30, 2026

Study Record Updates

• Last Update Posted (Actual): March 30, 2026
• Last Update Submitted That Met QC Criteria: March 24, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: caffeine; ergogenic aids; cycling; dietary nitrate; beetroot juice; exercise physiology; critical power,
• Additional Relevant MeSH Terms: Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Alkaloids; Purinones; Purines; Xanthines; Caffeine
• Other Study ID Numbers: IRB-20-170

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No