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

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).

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