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Completed

NCT Number: NCT07479875

Caffeine Supplementation and Strength Endurance in Brazilian Jiu-jitsu Athletes

This study investigated the acute effects of ingesting 400 mg of caffeine administered 30 minutes before Brazilian jiu-jitsu-specific strength endurance tests. Experienced athletes completed two conditions, placebo and caffeine, in a randomized, double-blind, crossover clinical trial. Performance was assessed using the dynamic component of the kimono grip strength test (maximum number of repetitions, MNR) and the isometric component (maximum static lift, MSL), both performed with a gi grip. Rating of perceived exertion, adverse effects, and blinding effectiveness were also evaluated.

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Key information

Conditions

Muscle Strength Behavior Exercise Motor Activity Physical Endurance

Age range

18 year–35 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Universidade Federal de Minas Gerais (UFMG), Laboratory of Nutrition and Exercise Training (LAN-UFMG), Belo Horizonte, MG, Brazil

Belo Horizonte, Minas Gerais, 31275000, Brazil

About this study

Caffeine is a widely used ergogenic aid in combat sports due to its effects on alertness, strength, and muscular endurance. This study evaluated whether an absolute dose of 400 mg of caffeine, ingested 30 minutes before testing, improved performance in Brazilian jiu-jitsu-specific strength endurance tests performed with a gi grip.

Fifteen experienced athletes completed two experimental sessions separated by at least seven days in a randomized, double-blind, crossover design. In each session, participants performed three maximal sets of the dynamic component of the kimono grip strength test (maximum number of repetitions, MNR) and three trials of the isometric component (maximum static lift, MSL). Dietary intake was controlled during the 24 hours preceding each session, and athletes were instructed to avoid stimulant substances.

Adverse effects were monitored for 24 hours following each session, and blinding effectiveness was assessed using the Bang blinding index. The study also examined interindividual variability in response to caffeine supplementation.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adult men
  • Brazilian Jiu-Jitsu athletes
  • Minimum of 5 years of continuous practice
  • Participation in competitions within the past 12 months
  • Absence of upper-limb injuries
  • No use of caffeine or stimulant substances within 48 hours prior to testing
  • Availability to attend both experimental sessions
  • Physical fitness to perform maximal strength tests

Exclusion criteria

  • Recent musculoskeletal injuries
  • Use of stimulant substances, pre-workout supplements, or thermogenic products
  • Known hypersensitivity to caffeine
  • Clinical conditions that could limit participation (cardiovascular, respiratory, or neurological)
  • Failure to attend any experimental session
  • Noncompliance with pre-test nutritional guidelines

Treatment and study plan

Caffeine

Dietary Supplement

Capsule containing 400 mg of anhydrous caffeine ingested 30 minutes before performance testing.

Other names: caf

Placebo

Other

Capsule containing 400 mg of cornstarch used as placebo, ingested 30 minutes before performance testing.

Primary outcomes

  1. Dynamic component of the Kimono Grip Strength Test (Maximum Number of Repetitions, MNR)

    Time frame: During each experimental session, following intervention administration (two sessions, approximately 7 days apart).

    Brazilian jiu-jitsu-specific strength endurance test performed using a kimono grip on a pull-up bar. Participants completed three maximal sets of the dynamic component of the Kimono Grip Strength Test (maximum number of repetitions, MNR), and the total number of valid repetitions was recorded.

  2. Isometric component of the Kimono Grip Strength Test (Maximum Static Lift, MSL)

    Time frame: During each experimental session, following intervention administration (two sessions, approximately 7 days apart).

    Maximum isometric holding time (seconds) during the isometric component of the Kimono Grip Strength Test. Participants maintained an isometric position at approximately 90 degrees of elbow flexion using a kimono grip on a pull-up bar, and the maximal hold time was recorded.

Secondary outcomes

  1. Interindividual Response Variability

    Time frame: At study completion, after the second experimental session (two sessions approximately 7 days apart).

    Performance difference between caffeine and placebo conditions (CAF - placebo). A responder was defined as an improvement of ≥1 repetition in the dynamic component of the Kimono Grip Strength Test (maximum number of repetitions, MNR) or ≥1 second in the isometric component (maximum static lift, MSL).

  2. Rating of perceived exertion (Borg CR10 scale)

    Time frame: During each experimental session, at the end of testing following intervention administration (two sessions, approximately 7 days apart).

    Global perceptual assessment of effort using the Borg Category-Ratio 10 Scale (CR10). The scale ranges from 0 to 10, where 0 indicates no exertion and 10 indicates maximal exertion. Higher scores represent greater perceived effort.

  3. Bang blinding index

    Time frame: At the end of each experimental visit following intervention administration (two visits, approximately 7 days apart).

    Blinding effectiveness assessed using the Bang blinding index. The index ranges from -1 to +1, where values near 0 indicate successful blinding, positive values indicate correct identification of the assigned intervention, and negative values indicate incorrect guesses.

  4. Acute Adverse Effects

    Time frame: Within 24 hours after each experimental session following intervention administration (two sessions, approximately 7 days apart).

    Self-reported symptom questionnaire completed 24 hours after each experimental session, including tremor, anxiety, nausea, headache, insomnia, and tachycardia.

Sponsors and collaborators

Lead sponsor

Federal University of Minas Gerais

Other

Collaborators

  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.

Registry information

Acronym: CAF-BJJ

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Mar 18, 2026
Registry last updated
Mar 18, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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