Caffeine enhances endurance performance by blocking adenosine receptors, reducing perceived exertion, and improving substrate utilisation. A 70kg rider's sweet spot is 210-420mg — roughly 2-4 espressos or a sports-nutrition capsule. Habitual caffeine users see smaller acute benefits; cycling through a 5-7 day washout before key events restores responsiveness. Anecdotal tolerance varies widely. Dose timing matters: for longer events, an initial dose plus smaller top-ups every 2-3 hours is more effective than a single large dose.