Effects of an Acute Dose of Caffeine on the Performance of CrossFit Athletes

Not Applicable

Completed

• Conditions: Healthy, Young Adults; Athletic Performance

• Registration Number: NCT06891469
• Lead Sponsor: Democritus University of Thrace

Brief Summary

The goal of this clinical trial was to investigate the effect of an acute dose of caffeine on CrossFit performance in young, healthy male CrossFit athletes. The main questions it aimed to answer were whether an acute dose of caffeine, compared to placebo:

* Can improve performance in a specific CrossFit workout

* Leads to a reduction in the Rating of Perceived Exertion

* Leads to an increase in blood lactate concentration at the end of the workout

Participants had to:

* Complete two sessions of a specific CrossFit training program (four rounds of five exercises, 50 seconds of exercise/10 seconds of rest), 60 minutes after consuming either anhydrous caffeine (7.1 ± 0.7 mg/kg of body mass) or an equivalent amount of placebo, aiming to perform as many repetitions as possible.

* Report subjective perception of fatigue using the Borg scale at the end of each round.

Detailed Description

Preliminary measurements The preliminary measurements included anthropometry, body composition estimation, dietary and habitual caffeine consumption assessment. To assess habitual caffeine consumption, the volunteers were asked to answer a questionnaire through an interview, which investigated the typical consumption of specific caffeine-containing foods and beverages over the past month. Additionally, medical history information was collected through personal interviews.

Main tests Aerobic fitness and maximum heart rate were assessed using the 20-meter shuttle run at an indoor gymnasium. For each main session, the volunteers arrived at the gym having followed specific preparation instructions. Specifically, they were instructed to avoid intense exercise for 24 hours before the test, be hydrated, eat a carbohydrate-rich meal 3-4 hours earlier, avoid alcohol for 24 hours before the test, and refrain from energy drinks, supplements, or caffeine on the test day.

The two main tests were conducted at the same time of day and under similar environmental conditions for each volunteer. After being weighed, the volunteers took either caffeine or biotin capsules, and, 40 minutes later, they began warming up so that the training session would start 60 minutes after taking the supplement. Before the warm-up, blood lactate concentration was measured using the Lactate Scout 4 automatic lactate analyzer.

The volunteers executed five exercises (50 seconds on, 10 seconds off) for four rounds, aiming to perform as many repetitions as possible with the correct technique. The five exercises were push-ups, power cleans, front squats, sit-ups, and deadlifts. The power clean, front squat, and deadlift were performed with an external load of approximately 40%, 50%, and 60% of body weight, respectively.

Performance was defined as the total number of repetitions per round (i.e. the sum of repetitions in all exercises per round), as well as the number of repetitions performed in each exercise per round.

At the end of each round, the rating of perceived exertion (RPE) was recorded using the 6-to-20 Borg scale, and, one minute after the end of the workout, blood lactate concentration was measured again.

HR was monitored using a HR monitor (Polar H10) throughout the workout and averaged over each round.

Additionally, after completing the training sessions, the volunteers provided information about possible side effects (tachycardia, palpitations, feelings of anxiety/discomfort, headache, dizziness).

Study Timeline

• Study Start: 2022-01-22
• Primary Completion: 2022-05-29
• Study Completion: 2022-05-29
• Status Verified: 2025-03
• Study First Submitted: 2025-03-04
• Study First Submitted QC: 2025-03-17
• Last Update Submitted: 2025-03-22
• Study First Posted: 2025-03-25
• Last Update Posted: 2025-03-26

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 12

Inclusion Criteria

• Men
• Aged 18-40
• At least 2 years of experience with CrossFit programs
• Free of any medical condition that prevents the participant from performing the exercises of the training program at maximum capacity

Exclusion Criteria

• Consumption of caffeine and guarana supplements, unless were discontinued for at least two weeks before participating in the study

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Primary Outcome Measures

Name	Time	Method
Performance During CrossFit® Workout	After 5, 10, 15 and 20 minutes of exercise	Performance was defined as the total number of repetitions completed by the volunteers in the CrossFit program, the repetitions of all exercises per round, and the repetitions of each specific exercise per round.
Rating of Perceived Exertion during the CrossFit program	during the last 10 s of the 5th, 10th, 15th and 20th minute of exercise	Each partictipant had to record the subjective perception of fatigue, using the Borg scale (6 to 20, with higher score meaning feeling of higher exertion), at the end of each round of CrossFit program
Blood lactate concentration	1st measurement before the warm up and 2nd measurement one minute after the end of workout (i.e. after 20 min of exercise)	Blood lactate concentration was measured using the Lactate Scout 4 automatic lactate analyzer (EKF Diagnostics) in two time points: before the warm-up for CrossFit program and one minute after the end of the workout

Secondary Outcome Measures

Name	Time	Method
Heart Rate	Heart rate was measured every 1 second of exercise. For analysis, heart rate was averaged over the following time ranges: 1-5 , 6-10 , 11-15 and 16-20 minutes of exercise	Throughout the workout, heart rate was monitored using a heart rate monitor (Polar H10)
Aerobic fitness assessment	baseline (during the 2nd visit)	Maximum oxygen consumption was estimated using the 20-meter shuttle run test from the number of shuttles completed at exhaustion.
Maximum heart rate measurement	Heart rate was continuously recorded during the test (every 1 s), until exhaustion. The highest heart rate at the time of exhaustion was recorded.	Maximum Heart rate was determined during the 20-meter shuttle run test. Heart rate was continuously recorded using a heart rate monitor (Polar H10).

Trial Locations

Locations (1)

Stefanos Karalis Indoors Facilities; 🇬🇷 Athens, Byron, Greece