Supplements - caffeine for runners, OCR athletes, and endurance training

How caffeine affects performance and recovery for running, OCR, and endurance sports

Thomas Solomon, PhD.

Updated on October 31, 2025
Reading time approx 7 minutes (1400 words).

What you’ll learn:

Caffeine is a stimulant that acts on your brain and your metabolism.

Taking caffeine before or during a session or race can meaningfully boost endurance, strength, and speed performance.

It helps even if you’re a regular caffeine user.

Curious about the how and why? Scroll down for the details, the nuances, and the nerdy bits.

The information I provide is not medical advice. Caffeine can have side effects and might interact with other drugs, nutrients, and medical conditions (see here). If you are unsure, always consult your doctor to ensure that a specific supplement is safe for you to use.

What is caffeine?

Caffeine (1,3,7-trimethylxanthine) is a psychoactive stimulant. In simple terms, it blocks adenosine receptors in the brain. Adenosine usually tells your body to relax and dial things down; caffeine gets in the way of that message so “go” chemicals like dopamine can keep doing their thing. Caffeine may also influence calcium transport in muscle cells, but the main show is in the central nervous system.

Side effects can include a faster heart rate, palpitations, headache, trouble sleeping, peeing more, jitters, and stomach upset. If you notice any of these before, during, or after training or racing, you’ve probably gone a bit heavy on the dose. Given those side effects — and the media headlines about super-sugary energy drinks — it’s fair to ask: is caffeine dangerous?

A 2017 systematic review concluded that “up to 400 milligrams of caffeine per day in healthy adults is not associated with overt adverse effects” and that up to 300 milligrams per day is generally safe in healthy pregnant women.

A 2017 umbrella review of meta-analysesA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment. found that “coffee consumption seems generally safe within usual levels of intake”. In sport settings, a 2022 systematic review reported that athletes should weigh both benefits and risks and that “around 3 milligrams per kilogram bodyweight may balance performance gains with fewer side effects”.

And in everyday life, a 2023 randomised controlled crossover trial with continuous ECG monitoring found that drinking more caffeinated coffee than usual may increase premature ventricular contractions, but did not the number of unusual heart rhythms (atrial arrhythmias) in healthy adults (Marcus et al.).

So, the bottom line, caffeine is generally safe for most people if used within the recommended amounts.

Therefore, it is no surprise that a lot of people use caffeine as a way to start (and continue) their day. Bonjour coffee! The NHANESstudy found that roughly 89% of US adults consume caffeine daily, and a 2022 survey found that 85% of endurance athletes reported daily caffeine consumption and 41% reported multiple daily caffeine intake, though fewer (24%) used purpose-made caffeine supplements during training or racing. So…

What is the scientific evidence on caffeine’s impact on athletic performance?

RightArrow Taking caffeine 60 to 90 minutes before exercise — or before and during exercise — lowers the RPERPE means “rating of perceived exertion,” a simple 0 to 10 or 6 to 20 scale for how hard the effort feels. Lower RPE means the same work feels easier. during exercise (moderate effect sizeAn effect size is a quantitative measure of the magnitude of a relationship or difference between groups in a study. Unlike p-values, effect sizes show how large or meaningful that effect is. Common effect size measures include Cohen’s d, Hedges’ g, eta-squared, and correlation coefficients.), including during long, hard efforts (moderate to large effect size).

RightArrow It improves endurance performance in time trials and time-to-exhaustion tests (moderate effect size), increases muscle strength (moderate effect), helps raise jump height (small effect), and boosts maximal power in very short efforts (small to moderate effect).

RightArrow In the heat (about 30 degrees Celsius or hotter), pre-exercise caffeine still helps with endurance exercise with only a trivial extra heat stress to core temperature changes from the workout itself.

RightArrow In skill-based and team sports, caffeine can shave time off agility tests (moderate effect) and increase total running distance, sprint running distance, and the number of sprints during matches (small to moderate effects).

RightArrow Most performance studies test people when they’re fresh. We don’t yet know if the same boost happens when tests come after a fatiguing bout of exercise.

RightArrow The effect is usually bigger for aerobic-type efforts than for pure “anaerobic” bursts.

RightArrow Adding caffeine to carbohydrate during endurance exercise gives a small extra performance boost compared with carbohydrate alone.

RightArrow Female participants are under-represented in caffeine research (see here and here). Some meta-analyses report performance benefits in females (see here, here, and here) but further research is needed to tailor advice.

RightArrow Caffeine metabolism depends mostly on the enzyme cytochrome P450 1A2, coded by the CYP1A2 gene. Sorry, that’s a bit jargonny, but people with different CYP1A2 genotypes metabolize caffeine faster or slower. That might change the performance boost — some studies find “fast” metabolizers (AA genotype) benefit more — but results are small and inconsistent. More research is needed.

RightArrow Caffeine mouth-rinsing has mixed results. Some studies say “yay”, but many studies say “nay” for performance. Swallowing caffeine is the reliable route.

RightArrow You might wonder: Does coffee have the same performance-enhancing effect as isolated caffeine? When coffee vs. pure caffeine is matched for caffeine dose, coffee works similarly (see ISSN position stand 2023). The headache is knowing the actual amount of caffeine in your coffee cup. The “average” cup of coffee is said to contain approximately 100 milligrams of caffeine. Since the performance-enhancing dose of caffeine is within 3 to 6 milligrams per kg bodyweight, 2-cups of coffee (~200 milligrams of caffeine) “should” provide ~3 milligrams per kg of caffeine for a person weighing 70 kg. However, bean type, brew method, and cup size swing the dose wildly, so 100 mg per cup is a (bad) guess at best. For training, the “2 cups = performance boost” rule of thumb can be fine. For race day, a sports product with a known caffeine amount is safer.

RightArrow You might also wonder: Does chronic caffeine use alter caffeine’s acute performance-enhancing effects? A 2019 review argued that habitual caffeine may blunt the boost a little, but slightly higher acute doses can restore it. They authors also noted that short-term caffeine/coffee withdrawal before a key event doesn’t seem to add extra benefit from supplemental caffeine. They also made the highly relevant point that “Given the individual response to caffeine, both in terms of habituation and ergogenesis, athletes should experiment with various doses and timing strategies when using caffeine to enhance performance”. In other words, always experiment with dose and timing in training before unleashing your caffeine buzz on race day.

RightArrow Caffeine can reduce sleep quality and duration (see here and here). To protect sleep, aim to finish coffee about 9 hours before bedtime and caffeine-containing supplements about 13 hours before bedtime (see here).

RightArrow Anti-doping note: caffeine is widely used, socially accepted, generally safe, and hard to regulate. Yes, caffeine is so potent it might be banned if discovered today but caffeine-containing plants have been used by humans since the dawn of breakfast. Consequently, in the eyes of World Anti-Doping Agency (WADA), caffeine is a a “monitored” substance but does not ban it. Always check your sport’s rules and the latest WADA prohibited list and your event’s policies.

RightArrow If you choose to use caffeine, a reasonable dose is:

3 to 6 milligrams (mg) of caffeine per kg body weight 30 to 60-minutes before a session or race. Note: this is based on effective doses used in research. Click here to see some examples of caffeine-containing gels).

That’s roughly 1 to 2 cups of coffee — but the true caffeine in a cup varies a lot by bean, brew, and cup size.

Taking more doesn’t necessarily mean a bigger effect; taking more increases the risk of side effects.

The verdict:

Can caffeine enhance athletic performance?

Taking caffeine before a race or session is likely to improve performance during endurance, strength, and speed-based events.

Taking caffeine during exercise is also likely to boost performance, but there is insufficient evidence to recommend a specific repeated caffeine dosing regimen during exercise.

The effect sizeAn effect size is a standardized measure of the magnitude of an effect of an intervention. Unlike p-values, effect sizes show how large the effect is and indicate how meaningful it might be. Common effect size measures include standardised mean difference (SMD), Cohen’s d, Hedges’ g, eta-squared, and correlation coefficients. ranges from small (for short, high/maximal-intensity efforts) to moderate/large (for endurance).

The effects of caffeine appear to be similar between trained athletes and untrained folks, and between males and females.

These conclusions are based on a moderateA moderate quality of evidence means that, in general, studies in this field have some limitations. This could be due to somewhat inconsistent effects between studies, a moderate range of effect sizes between studies, and/or a moderate risk of bias (caused by a small to medium number of studies, small to medium numbers of participants, partially described randomization processes, some missing data, some inappropriate methods/statistics). When the quality of evidence is moderate, there is some doubt and only moderate confidence in the overall effect of an intervention, and future studies could change overall conclusions. The best way to improve the quality of evidence is for scientists to conduct large, well-controlled, high-quality randomized controlled trials. to high quality of evidenceA high quality of evidence means that, in general, there is a small range of effect sizes between studies, effects are consistent, and there is a low risk of bias (due to a large number of studies, large numbers of participants, good study designs, appropriate methods, etc). When the quality of evidence is high, there is a high level of confidence that the overall effect size reflects the true effect.: effects are fairly consistent between studies, and there’s a large number of well-designed studies. Consequently, there’s a high level of confidence that the overall effect sizes reported in meta-analysesA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment. reflect the true effect of caffeine.

To minimise the risk of consuming a supplement that contains prohibited substances, only choose products that have been independently tested (e.g., Informed Sport). And, remember: Supplements do not make athletes and do not replace training; they're just the icing on a very well-baked cake. Before reaching for pills and potions, optimise your training load and dial in your sleep, nutrition, and rest.

How to use this: In training, try 3 to 6 milligrams per kilogram bodyweight (roughly 200 to 400 milligrams in a 70 kg person) 30 to 60 minutes pre-session and note your response (performance gains, gut issues, and sleep problems). For race day, prefer products with known caffeine amounts rather than guessing with coffee. If you’re a habitual caffeine user, you might need the upper end of that range — but don’t chase more, because side effects climb quickly. To protect sleep, finish coffee at least 9 hours before bed and caffeine-containing supplements at least 13 hours before bed. And, keep it legal: always check your event’s rules and the current WADA prohibited list.

important The information I provide is not medical advice. Caffeine can have side effects (see here) and might interact with other drugs, nutrients, and medical conditions (see here). If you are unsure, always consult your doctor to ensure that a specific supplement is safe for you to use.

Full list of meta-analyses examining caffeine for performance.

Here are the meta-analyses I've summarised above:

Caffeine for runners, OCR, and endurance athletes from Thomas Solomon

Strengthen the fight for Clean Sport:

right arrow Consult WADA’s prohibited list, cross-check your meds against the Global DRO drug reference list, and only choose supplements that have been tested by an independent body (e.g., Informed Sport or LabDoor).

right arrow Remember: You are the only person responsible for what goes in your body! Ignorance is not an excuse! Stay educated. Be informed.

right arrow And, always aim to nail your daily nutrition habits first, then layer specific sports nutrition on top of that, and then start to consider supplements.

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”alert” Disclaimer: I occasionally mention brands and products, but it is important to know that I don't sell recovery products, supplements, or ad space, and I'm not affiliated with / sponsored by / an ambassador for / receiving advertisement royalties from any brands. I have conducted biomedical research for which I’ve received research money from publicly-funded national research councils and medical charities, and also from private companies, including Novo Nordisk Foundation, AstraZeneca, Amylin, the A.P. Møller Foundation, and the Augustinus Foundation. I’ve also consulted for Boost Treadmills and Gu Energy on R&D grant applications, and I provide research and scientific writing services for Examine.com. Some of my articles contain links to information provided by Examine.com but I do not receive any royalties or bonuses from those links. Importantly, none of the companies described above have had any control over the research design, data analysis, or publication outcomes of my work. I research and write my content using state-of-the-art, consensus, peer reviewed, and published scientific evidence combined with my empirical evidence observed in practice and feedback from athletes. My advice is, and always will be, based on my own views and opinions shaped by the scientific evidence available. The information I provide is not medical advice. Before making any changes to your habits of daily living based on any information I provide, always ensure it is safe for you to do so and consult your doctor if you are unsure.