Sports Nutrition
Caffeine and athletic performance: the evidence
Caffeine is one of the very few supplements with genuinely strong, consistent evidence behind it — and one of the easiest to get wrong by overdoing.
How much, and when
The International Society of Sports Nutrition's position stand concludes that caffeine improves performance across endurance, high-intensity, and strength-based activities at doses of roughly 3–6 mg per kg of body weight, taken about 60 minutes before exercise. For a 70 kg athlete that's around 210–420 mg — roughly two to four cups of coffee.[1]
Higher doses (9 mg/kg and above) do not reliably improve performance further, and markedly increase side effects: jitteriness, elevated heart rate, GI upset, and disrupted sleep.[1]
What it actually does
The main mechanism isn't extra energy — caffeine has no calories. It blocks adenosine receptors in the brain, which reduces your perception of effort and fatigue, so a given workload feels easier. That's why the effect shows up most clearly in endurance events and in sustained high-intensity work.[1]
Individual response varies a lot
Genetic differences in caffeine metabolism, plus habitual intake, mean the same dose affects people very differently. Response is worth testing in training rather than on competition day.[1]
Caffeine's effect on sleep is the most common way athletes undermine themselves with it — and sleep loss degrades recovery and performance more than the caffeine helped.
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