Caffeine Supplementation and Strength Endurance in Brazilian Jiu-jitsu Athletes (CAF-BJJ)

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.

Study Overview

• Status: Completed
• Conditions: Exercise; Muscle Strength; Physical Endurance
• Intervention / Treatment: Other: Placebo; Dietary supplement: Caffeine

Detailed Description

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.

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

Contacts and Locations

Study Locations

• Brazil
  • Minas Gerais
    • Belo Horizonte, Minas Gerais, Brazil, 31275000
      • Universidade Federal de Minas Gerais (UFMG), Laboratory of Nutrition and Exercise Training (LAN-UFMG), Belo Horizonte, MG, Brazil

Participation Criteria

Eligibility Criteria

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

Description

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

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Capsule containing 400 mg of starch (placebo), ingested 30 minutes before testing.	Other: Placebo; Capsule containing 400 mg of cornstarch used as placebo, ingested 30 minutes before performance testing.
Experimental: Caffeine; Capsule containing 400 mg of anhydrous caffeine, ingested 30 minutes before testing.	Dietary supplement: Caffeine; Capsule containing 400 mg of anhydrous caffeine ingested 30 minutes before performance testing.; Other Names: caf

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dynamic component of the Kimono Grip Strength Test (Maximum Number of Repetitions, MNR)	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.	During each experimental session, following intervention administration (two sessions, approximately 7 days apart).
Isometric component of the Kimono Grip Strength Test (Maximum Static Lift, MSL)	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.	During each experimental session, following intervention administration (two sessions, approximately 7 days apart).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Interindividual Response Variability	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).	At study completion, after the second experimental session (two sessions approximately 7 days apart).
Rating of perceived exertion (Borg CR10 scale)	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.	During each experimental session, at the end of testing following intervention administration (two sessions, approximately 7 days apart).
Bang blinding index	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.	At the end of each experimental visit following intervention administration (two visits, approximately 7 days apart).
Acute Adverse Effects	Self-reported symptom questionnaire completed 24 hours after each experimental session, including tremor, anxiety, nausea, headache, insomnia, and tachycardia.	Within 24 hours after each experimental session following intervention administration (two sessions, approximately 7 days apart).

Collaborators and Investigators

• Sponsor: Federal University of Minas Gerais
• Collaborators: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.

Study record dates

Study Major Dates

• Study Start (Actual): December 12, 2025
• Primary Completion (Actual): January 15, 2026
• Study Completion (Actual): January 15, 2026

Study Registration Dates

• First Submitted: November 20, 2025
• First Submitted That Met QC Criteria: March 14, 2026
• First Posted (Actual): March 18, 2026

Study Record Updates

• Last Update Posted (Actual): March 18, 2026
• Last Update Submitted That Met QC Criteria: March 14, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Double-Blind; Grip Strength; Caffeine; Athletes; Muscular Endurance; Ergogenic Aid; Combat Sports; Randomized Crossover Trial; Brazilian Jiu-Jitsu
• Additional Relevant MeSH Terms: Behavior; Motor Activity; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Alkaloids; Purinones; Purines; Xanthines; Caffeine
• Other Study ID Numbers: 8.062.851

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared due to ethical and confidentiality restrictions, as participants did not provide consent for public data sharing. Aggregated data are available in the published study reports.

Drug and device information, study documents

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