Exercise, Muscle Strength, Physical Endurance
Conditions
Keywords
Caffeine, Ergogenic Aid, Brazilian Jiu-Jitsu, Combat Sports, Muscular Endurance, Grip Strength, Athletes, Randomized Crossover Trial, Double-Blind
Brief summary
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.
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.
Interventions
DIETARY_SUPPLEMENTCaffeine
Capsule containing 400 mg of anhydrous caffeine ingested 30 minutes before performance testing.
OTHERPlacebo
Capsule containing 400 mg of cornstarch used as placebo, ingested 30 minutes before performance testing.
Sponsors
Federal University of Minas Gerais
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior.
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
Caffeine and placebo capsules were identical in color, size, shape, and taste. Randomization was performed by a researcher not involved in data collection. Neither the participants nor the assessors were aware of which substance was administered in each session. The allocation code was revealed only after the completion of the data analysis.
Intervention model description
Brazilian Jiu-Jitsu athletes completed two experimental sessions in a randomized, double-blind, crossover design. In one session, participants ingested caffeine, and in the other, they ingested a placebo, with a minimum washout period of seven days. The order of the conditions was counterbalanced across participants, and all performance assessments were conducted under both conditions.
Eligibility
Sex/Gender
MALE
Age
18 Years to 35 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Dynamic component of the Kimono Grip Strength Test (Maximum Number of Repetitions, MNR) | 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. |
| Isometric component of the Kimono Grip Strength Test (Maximum Static Lift, MSL) | 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
| Measure | Time frame | Description |
|---|---|---|
| Interindividual Response Variability | 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). |
| Rating of perceived exertion (Borg CR10 scale) | 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. |
| Bang blinding index | 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. |
| Acute Adverse Effects | 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. |
Countries
Brazil
Outcome results
None listed