An interventional study of Caffeine in Athletic Performance, Caffeine and Wrestling, sponsored by Islamic Azad University, Abadan Branch. Completed at 1 site in Iran. Open to male participants aged 15 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-22.
Sponsored by Islamic Azad University, Abadan Branch · Not applicable, Interventional, and Other
Caffeine is commonly used by athletes to improve performance, but not everyone responds to it in the same way. In weight-class sports like wrestling, athletes are grouped by body weight. When caffeine is dosed based on body weight (4 mg per kg), heavier athletes receive a larger total amount of caffeine than lighter athletes. This study asked whether the effects of caffeine on wrestling performance and side effects differ across wrestling weight classes.
Ninety-five male wrestlers (30 lightweight, 36 middleweight, and 29 heavyweight) completed two testing sessions: one after taking caffeine (4 mg/kg) and one after taking a placebo (an inactive capsule). Neither the wrestlers nor the researchers knew which capsule was given in each session. Each session included a countermovement jump test and a wrestling-specific fitness test that involved throwing a wrestling dummy. Heart rate, perceived exertion, and self-reported symptoms were also recorded.
The study found that lightweight and middleweight wrestlers generally performed better after caffeine, while heavyweight wrestlers showed no performance improvement and reported more side effects, such as anxiety, rapid heartbeat, stomach discomfort, and insomnia. These differences occurred even though all wrestlers received the same caffeine dose relative to their body weight.
The results suggest that a standard body-weight-based caffeine dose may not work equally well for all wrestlers. Lighter wrestlers may benefit more, while heavier wrestlers may experience more side effects without performance gains. These findings support the need for individualized caffeine dosing strategies in wrestling and similar weight-class sports. However, because body weight, total caffeine dose, and other weight-class-related factors were not separated in this study, the results should be considered exploratory and do not establish weight-specific recommendations.
This is the only study on the registry with Islamic Azad University, Abadan Branch as lead sponsor.
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Participants in this arm received a caffeine capsule (4 mg/kg body mass) in the first experimental session and a placebo capsule (dextrose) in the second experimental session, with a 1-week washout period between sessions. Capsules were administered 60 minutes before performance testing. Participants completed countermovement jump testing and the Special Wrestling Fitness Test (SWFT) in each session.
Drug: Caffeine
Participants in this arm received a placebo capsule (dextrose) in the first experimental session and a caffeine capsule (4 mg/kg body mass) in the second experimental session, with a 1-week washout period between sessions. Capsules were administered 60 minutes before performance testing. Participants completed countermovement jump testing and the Special Wrestling Fitness Test (SWFT) in each session.
Drug: Caffeine
Anhydrous caffeine powder (Sigma-Aldrich, Steinheim, Germany) encapsulated in identical opaque gelatin capsules. Administered orally at a dose of 4 mg/kg body mass with approximately 200 mL of water, 60 minutes before performance testing.
Total number of throws (Tn)
Total number of successful throws completed across the three active periods of the Special Wrestling Fitness Test (SWFT). A throw was considered correct only when it satisfied the technical scoring criteria of United World Wrestling. Three independent assessors counted the throws, with discrepancies resolved through discussion.
Time frame: Measured during each experimental session, 60 minutes after supplementation.
Performance Index (PI)
A wrestling-specific performance index calculated as (HR0 + HR1) / Tn, where HR0 is heart rate immediately after the SWFT and HR1 is heart rate 1 minute after the SWFT. A lower performance-index value indicates a greater number of throws relative to the recorded cardiac response.
Time frame: Measured during each experimental session, 60 minutes after supplementation.
Body-mass-normalized throws (TnW)
Total number of throws normalized to body weight, calculated as Tn divided by body weight in kilograms (TnW = Tn / body weight). This outcome reflects wrestling-specific work relative to body weight and has shown strong predictive validity for wrestling performance.
Time frame: Measured during each experimental session, 60 minutes after supplementation.
Countermovement jump performance
Lower-body explosive power assessed using the Sargent vertical jump test (wall-mounted reach method). Participants performed three maximal countermovement jumps with 60 s passive recovery between attempts. Jump height (cm) was calculated as the difference between standing reach and maximal jump reach. The highest value was retained for analysis.
Time frame: 60 minutes after supplementation, before the Special Wrestling Fitness Test (SWFT).
Rating of perceived exertion (RPE)
Overall perceived exertion during the SWFT, assessed using the 10-point Borg scale immediately after the test.
Time frame: Immediately after the SWFT.
Self-reported symptoms on the test day
Presence or absence of negative symptoms assessed using an adapted QUEST checklist: anxiety, headache, dizziness, nervousness, irritability, tachycardia, abdominal discomfort, increased urine output, muscle soreness, and fatigue. Each item recorded dichotomously (yes/no). Vigor/activeness was treated separately as a positive self-reported effect and excluded from the adverse-symptom composite.
Time frame: Immediately after each testing session (test day).
Self-reported symptoms on the following day
Presence or absence of negative symptoms including insomnia, assessed 24 hours after each testing session using the same adapted QUEST checklist.
Time frame: 24 hours after each testing session.
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Plan to share: Yes
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Analytic code
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is completed, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Caffeine