What is caffeine?
Caffeine is a methylxanthine alkaloid found naturally in coffee, tea, cocoa, and guarana. It is the most consumed psychoactive substance in the world and has decades of research confirming its ergogenic effects across endurance, strength, and cognitive performance.
How it works
Caffeine works primarily by blocking adenosine receptors in the brain. Adenosine is a neurotransmitter that promotes drowsiness — by blocking its receptors, caffeine prevents the perception of fatigue. It also increases adrenaline release, elevates heart rate, and enhances the mobilisation of fatty acids as fuel. In muscle tissue, it improves calcium release from the sarcoplasmic reticulum, directly enhancing contractile force.
What the research says
- 3–6mg per kg bodyweight improves endurance performance by 2–4% on average (Ganio et al., 2009)
- Significant improvements in muscular endurance and one-rep max strength at effective doses
- Reduces perceived exertion during exercise — the same effort feels easier
- Improves reaction time, focus, and cognitive performance under fatigue
- Tolerance develops with regular use — cycling caffeine preserves its effectiveness
Effective dose
3–6mg per kg of bodyweight taken 30–60 minutes before exercise. For a 80kg person this is 240–480mg. Most pre-workouts contain 150–350mg per serve. Doses above 6mg/kg increase side effects without additional performance benefit. Caffeine-naive individuals should start at the lower end.
What to check on the label
Check total caffeine per serve including all sources — caffeine anhydrous, guarana extract, green tea extract, and green coffee bean extract all contribute to total caffeine load. Some products list caffeine from multiple sources separately, making the total unclear. Add them all together before assessing the dose.
Safety
Safe for healthy adults at doses up to 400mg per day. Side effects at higher doses include anxiety, elevated heart rate, insomnia, and gastrointestinal discomfort. Caffeine has a half-life of approximately 5 hours — a 300mg dose at 4pm still has 150mg active at 9pm. Avoid within 6–8 hours of intended sleep time.