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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
15
Universidade Federal de Minas Gerais (UFMG), Laboratory of Nutrition and Exercise Training (LAN-UFMG), Belo Horizonte, MG, Brazil
Belo Horizonte, Minas Gerais, Brazil
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.
Time frame: 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.
Time frame: During each experimental session, following intervention administration (two sessions, approximately 7 days apart).
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).
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: Within 24 hours after each experimental session following intervention administration (two sessions, approximately 7 days apart).
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