Caffeine and athletic performance: What research shows about timing, dosage and habituation

Caffeine belongs to the methylxanthine group and is pharmacologically a competitive antagonist at adenosine receptors — primarily the A1 and A2A subtypes in the central nervous system. This mechanism explains most of its performance-relevant effects.

Adenosine is an endogenous nucleoside that continuously accumulates in the brain, the longer we are awake and the more intensely we exercise. It binds to A1 and A2A receptors, where it produces inhibitory effects: drowsiness, reduced neurotransmitter release and increased pain sensitivity.

Caffeine and adenosine share a structural similarity as purine derivatives. This allows caffeine to bind competitively to the same receptors without triggering the typical adenosine response. It blocks the receptor for as long as it remains bound.

What this means in training practice: Fatigue and exercise intensity are perceived as less severe. RPE (Rate of Perceived Exertion) falls despite the same objective workload. At the same time, dopamine and noradrenaline can be released more strongly, as adenosine normally inhibits their release.

At higher doses (above 6 mg/kg), caffeine also inhibits phosphodiesterase, preventing the breakdown of cyclic AMP (cAMP). Elevated cAMP levels activate hormone-sensitive lipase in fatty tissue and promote lipolysis — a metabolic effect that may be particularly relevant during endurance exercise lasting more than 90 minutes.

A third mechanism directly affects muscle physiology: caffeine modulates calcium release from the sarcoplasmic reticulum, increasing the contractile force of individual muscle fibres.

Among all legal ergogenic substances, the evidence for caffeine is among the most robust. The International Society of Sports Nutrition (ISSN) Position Stand (Grgic et al., 2021) concludes that caffeine at a dose of 3–6 mg/kg significantly improves aerobic endurance performance, with moderate effect sizes between 0.3 and 0.5.

Endurance performance benefits most: Timed efforts lasting from 1 to 60 minutes consistently show improvements of 2–4%, and by up to 9% versus placebo in individual studies. The effect has been demonstrated in cyclists, runners and triathletes alike.

Strength performance: A 2025 meta-analysis (PMC) confirms that caffeine produces statistically significant improvements in mean power output and maximal strength during resistance exercise. The effect is moderate but reliably reproducible, particularly for upper-body exercises.

Cognitive performance is an often underestimated factor. Reaction time, decision-making speed and focus demonstrably improve — relevant in technically demanding sports such as badminton, climbing or mountain biking.

A study published in 2025 (Frontiers in Nutrition) involving elite badminton players showed that acute caffeine intake significantly improved both sport-specific and cognitive parameters.

Not ideal if: The response to caffeine is highly individual. CYP1A2 polymorphisms — genetic variants of the enzyme responsible for caffeine metabolism — determine whether someone is a fast or slow metaboliser. Slow metabolisers (around 40–50% of the population) have shown a smaller ergogenic effect in some studies and face a higher cardiovascular risk at high doses.

The most commonly used and recommended dose is 3–6 mg per kilogram of body weight. Below 3 mg/kg, the effects are smaller and less consistent. Above 6 mg/kg, side effects increase without any further improvement in performance.

Until 2004, caffeine was on the WADA doping list when certain urine concentrations were exceeded. It is no longer prohibited today, but the World Anti-Doping Agency continues to include it in its monitoring programme. From around 12 mg/kg, heart rate and blood pressure rise sharply; such doses are considered medically problematic.

In practice: An athlete weighing 70 kg would aim for 210–420 mg of caffeine — roughly equivalent to two to four cups of filter coffee or a standardised caffeine supplement.

The classic recommendation is 45–60 minutes before training or competition. This is how long it takes to reach peak plasma concentration after taking caffeine capsules or coffee orally. The half-life is typically 5–6 hours, though it can be up to 9 hours in some people, known as slow CYP1A2 metabolisers.

However, the optimal timing varies according to the form:

• Caffeine capsules / coffee: 45–60 minutes before the start
• Caffeine gum: 10–15 minutes, as oral absorption speeds up uptake considerably
• Caffeinated energy gels: 30–45 minutes, depending on the formulation
• Caffeinated bars: 45–60 minutes, with gastric transit similar to capsules

Sleep timing is at least as important: with a caffeine half-life of 5–6 hours, 25% of the amount consumed is still circulating in the blood after 10–12 hours. Taking 300 mg at 14:00 leaves around 75 mg of active caffeine in your system at 20:00.

Studies show that caffeine measurably alters sleep architecture, particularly by reducing deep sleep and REM sleep, even when the subjective time taken to fall asleep is barely prolonged. Sleep may feel normal, but biochemically it is not.

Rule of thumb: stop consuming caffeine at least 8–9 hours before bedtime. During intensive training weeks or competition phases, this is an underestimated lever for better recovery.

The evidence on tolerance development is more nuanced than is often presented. Two lines of research offer seemingly contradictory findings:

Cross-sectional studies show that habitual coffee drinkers with high everyday intake respond similarly to acute caffeine supplementation as low consumers. This suggests that habituation does not completely eliminate the ergogenic effect.

Controlled crossover studies involving caffeine withdrawal for 4 to 28 days, by contrast, show that the effect is strongest on the first day after abstinence and decreases with continued daily intake. The effect measurably levels off after around one week.

This leads to a clear strategy for competition preparation: 4 days of complete caffeine abstinence before the key competition can significantly enhance the ergogenic effect. This approach is common in elite sport, although withdrawal symptoms may occur during the first 1–2 days: headaches, fatigue and reduced concentration.

The duration of effect also differs: in habitual consumers, improved performance typically lasts around 3 hours, compared with up to 6 hours in non-consumers.

Drinking caffeine every day to wake up while also using it as a pre-training supplement is suboptimal. It is not impossible, but the effect is reduced. If you want to use caffeine strategically as ergogenic support, manage your everyday intake consciously.

Caffeine is not a risk-free supplement, particularly at higher doses and for certain groups of people.

Cardiovascular system: At moderate to high doses, caffeine reduces coronary vasodilation during exercise. The heart receives less oxygen under high load. This is generally not a problem for healthy athletes, but caution is advised for people with coronary heart disease, cardiac arrhythmias, particularly atrial fibrillation, or uncontrolled high blood pressure.

Gastrointestinal tolerance: In 15–30% of endurance athletes, caffeine before training causes stomach discomfort, nausea or increased peristalsis. This occurs more often when caffeine is taken on an empty stomach and immediately before the start.

Pregnancy: EFSA recommends a total intake of less than 200 mg/day during pregnancy, including caffeine from all sources.

Interactions: Caffeine interacts with certain medicines. Fluoroquinolone antibiotics, such as ciprofloxacin, inhibit caffeine metabolism via CYP1A2 and can substantially increase plasma levels. Caution is also advised when taking MAO inhibitors.

Anxiety disorders and chronic sleep problems: Caffeine is an anxiogenic substance and can intensify anxiety and inner restlessness. If you are already prone to nervousness or have persistent sleep problems, weigh up its use carefully.