An interventional study of Caffeine 3 mg/kg and Caffeine 6 mg/kg in Caffeine, Athletic Performance and Resistance Traaining, sponsored by Birjand University of Medical Sciences. Completed at 1 site in Iran. Open to female participants aged 20 Years to 30 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-21.
Sponsored by Birjand University of Medical Sciences · Not applicable, Interventional, and Basic science
This study compares the effects of acute (single-session) and short-term (7-day) consumption of different doses of caffeine (3 and 6 mg/kg) on maximal strength, strength endurance, vertical jump, and medicine ball throw performance in habitual caffeine-consuming women (daily intake of 5 mg/kg). Thirty-six resistance-trained women were randomly assigned to three groups: 3 mg/kg caffeine, 6 mg/kg caffeine, or placebo in a double-blind crossover design. Participants completed both acute (60 min pre-exercise) and short-term (7 consecutive days) protocols. The main findings showed that acute ingestion of 6 mg/kg caffeine impaired peak power in the maximal strength test, while short-term consumption of the same dose improved peak power in the strength-endurance test. The 3 mg/kg dose was ineffective in all conditions. Caffeine did not affect jump or throw performance. The study highlights the need for individualized caffeine guidelines based on timing, dosage, and habituation status.
Absence of neuromuscular and musculoskeletal disorders
At least 2 years of regular resistance training experience (minimum 3 sessions per week)
At least 6 months of resistance training prior to enrollment
Absence of renal and hepatic disorders
Daily caffeine consumption of 5 mg/kg body weight (based on questionnaire)
No use of specific medications or supplements that could affect study outcomes (e.g., beta-alanine, creatine, pre-workout supplements) -
Exclusion Criteria:
Occurrence of any injury during the study
Failure to adhere to the supplement consumption protocol
Withdrawal from the study-
Participants received 3 mg/kg body weight of caffeine powder in gelatin capsules daily for 7 days. Acute consumption: 60 minutes before testing. Short-term consumption: 7 consecutive days
Dietary Supplement: Caffeine 3 mg/kg
Participants received 6 mg/kg body weight of caffeine powder in gelatin capsules daily for 7 days. Acute consumption: 60 minutes before testing. Short-term consumption: 7 consecutive days
Dietary Supplement: Caffeine 6 mg/kg
Participants received identical capsules containing flour, consumed daily for 7 days
Dietary Supplement: Placebo
Caffeine powder (99% purity) encapsulated in gelatin capsules at a dose of 3 mg per kilogram of body weight. The capsules are identical in appearance, odor, and taste to the placebo. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.
Caffeine powder (99% purity) encapsulated in gelatin capsules at a dose of 6 mg per kilogram of body weight. The capsules are identical in appearance, odor, and taste to the placebo. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.
Placebo capsules containing inert flour (or microcrystalline cellulose), identical in appearance, odor, and taste to the caffeine capsules. Participants consume the capsules daily for 7 consecutive days. On the testing day, the capsules are ingested 60 minutes prior to the exercise tests.
Change in Peak Power (PP) During Maximal Strength Test
Peak concentric power (Watts) during 1-RM bench press test, measured using a validated Kinect camera
Time frame: Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)
Change in Peak Power During Strength-Endurance Test
eak concentric power (Watts) during bench press at 50% of 1-RM to failure, measured using Kinect camera
Time frame: Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)
Change in Medicine Ball Throw Distance
Distance (cm) of 3-kg medicine ball throw from chest position
Time frame: Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)
Change in Vertical Jump Height
Countermovement jump height (cm) measured using Kinect camera
Time frame: Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)
Change in Number of Repetitions (Strength-Endurance)
Number of repetitions performed at 50% of 1-RM until failure
Time frame: Baseline, 60 minutes post-ingestion (acute), and after 7 days of supplementation (short-term)
Plan to share: No
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Birjand University of Medical Sciences