Caffeine — Supplements
Methylxanthine adenosine receptor antagonist with well-established ergogenic and cognitive-enhancing properties.
Overview
Caffeine is a methylxanthine that acts primarily as a competitive adenosine A1 and A2A receptor antagonist, promoting wakefulness, enhancing cognitive function, and improving physical performance. It is the most widely consumed psychoactive substance globally and has one of the strongest evidence bases of any ergogenic aid. Meta-analyses consistently demonstrate 2-4% improvements in endurance performance, enhanced strength and power output, and improved reaction time and vigilance. ISSN and IOC recognize caffeine as an effective ergogenic supplement.
Indications
- Cognitive performance and alertness
- Endurance exercise performance
- Strength and power output enhancement
- Reaction time improvement
- Fat oxidation during exercise
Mechanism of Action
Blocks adenosine A1 and A2A receptors, preventing adenosine-mediated sedation and promoting wakefulness
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| Caffeine | 200 mg | As needed (1-2x daily) | 3-6 mg/kg body weight for ergogenic effects; 60 min pre-exercise |
Safety & Contraindications
- Insomnia, anxiety, and tachycardia at higher doses (>400 mg/day)
- Tolerance develops with chronic use; periodic abstinence may restore sensitivity
- Withdrawal symptoms (headache, fatigue, irritability) begin 12-24 hours after cessation
- Avoid in pregnancy (limit <200 mg/day per ACOG) and anxiety disorders
- Genetic variation in CYP1A2 affects metabolism (slow vs. fast metabolizers)