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| Name | Class |
|---|---|
| Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior. | OTHER_GOV |
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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Placebo | Placebo Comparator | Capsule containing 400 mg of starch (placebo), ingested 30 minutes before testing. |
|
| Caffeine | Experimental | Capsule containing 400 mg of anhydrous caffeine, ingested 30 minutes before testing. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Caffeine | Dietary Supplement | Capsule containing 400 mg of anhydrous caffeine ingested 30 minutes before performance testing. |
|
| 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). |
| 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). |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Universidade Federal de Minas Gerais (UFMG), Laboratory of Nutrition and Exercise Training (LAN-UFMG), Belo Horizonte, MG, Brazil | Belo Horizonte | Minas Gerais | 31275000 | Brazil |
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.
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| ID | Term |
|---|---|
| D009043 | Motor Activity |
| ID | Term |
|---|---|
| D001519 | Behavior |
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| ID | Term |
|---|---|
| D002110 | Caffeine |
| ID | Term |
|---|---|
| D014970 | Xanthines |
| D000470 | Alkaloids |
| D006571 | Heterocyclic Compounds |
| D011688 | Purinones |
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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.
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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.
| Placebo | Other | Capsule containing 400 mg of cornstarch used as placebo, ingested 30 minutes before performance testing. |
|
| 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). |
| D011687 |
| Purines |
| D006574 | Heterocyclic Compounds, 2-Ring |
| D000072471 | Heterocyclic Compounds, Fused-Ring |