Everything Athletes Need To Know About Caffeine

Key points on caffeine and athletes:

  • Caffeine is without a doubt the most effective and legal endurance-enhancing
  • Thousands of published research articles demonstrate that caffeine can improve time trial performance, decrease time to fatigue, and make endurance exercise seem easier.
  • Effective dosing is 3-6 milligrams per kilogram body weight. Higher amounts do not increase endurance performance further.
  • Your 1st dose of caffeine should be taken ~60 minutes before endurance exercise. Additional caffeine can be taken every 2-3 hours after that.
  • Caffeine does not cause dehydration, and it won’t make your heart explode.
  • The research is conflicted as it relates to habituation to caffeine. If you feel it isn’t working as well after 3-4 weeks; abstain from caffeine for five days before taking again.

Caffeine Is An Effective Weapon In An Elite Endurance Athlete’s Arsenal

It’s no secret that the best endurance athletes in the world start their morning out with a cup of coffee or two before heading out the door for a workout or race.

Besides being the “best part of waking up,” and tasting damn fine, caffeine sparks several physiological processes in the body that can benefit both the elite endurance athlete and average joe alike.

This article will answer your most pressing questions about caffeine such as:

  1. How does it work to enhance endurance performance?
  2. How much should I take and when?
  3. What does the research say about caffeine?
  4. Is supplemental caffeine more effective than caffeine found in beverages such as coffee?
  5. And finally, are there any negative side effects?

A Brief Introduction to Caffeine:

Caffeine (1,3,7-trimethylxanthine) is the most widely consumed drug in the world and is commonly used by athletes, both recreational and professional, for performance enhancement.  

What Kind Of Products Contain Caffeine?

In the United States, over 70% of caffeine intake comes from coffee, followed by soft drinks and tea, although energy drinks and sports gels and chews containing caffeine are quickly gaining popularity for use before and during competition.

Caffeine is also frequently found in pre-workout supplements and weight loss products, often in multiple forms. 

With caffeine use so widespread among athletic populations, one must question its effectiveness regarding improving sports performance, and also whether there are any negative side effects from acute (short-term) or chronic (long-term) consumption.

What Happens In Your Body When You Take Caffeine?

Caffeine is absorbed rapidly by the gastrointestinal tract and enters the bloodstream within 15-45 minutes of consumption, with peak blood concentrations evident about one-hour post-ingestion. 

Its rapid absorption rate makes caffeine an effective endurance pre-workout supplement, since it doesn’t need to be “loaded” for days or weeks, and you can take it in a targeted manner just before a competition or training session.

Many consume caffeine for its effects as a central nervous system (CNS) stimulant in order to increase focus and alertness, but there is also evidence that the benefits of caffeine supplementation extend beyond these effects, specifically prolonged endurance, increased metabolic rate, enhanced fat metabolism, and improved neuromuscular function.

How Does Caffeine Work To Enhance Endurance Performance?

Caffeine is thought to work via three primary physiological mechanisms:

  1. Regarding giving you that awake and alive feeling, caffeine does this by competing with adenosine on adenosine receptors. Adenosine is a molecule when bound to its receptor, causes feelings of relaxation and sedation. Caffeine is very structurally similar to adenosine and thus can attach to the adenosine receptors as well. When this happens caffeine counteracts the adverse effects of adenosine on neurotransmission, arousal, and pain perception. Basically, it gives you that kick in the pants and makes intense endurance exercise seem easier than it should be.
  2. Caffeine may alter the release or uptake of calcium by the sarcoplasmic reticulum. The regulation of calcium controls muscular contractions, more specifically causing myosin to form a strong bond with actin filaments. Theoretically, if calcium release is increased from the sarcoplasmic reticulum, this could lead to longer and stronger muscle contractions = SUSTAINED ENDURANCE.
  3. Last but not least, caffeine is thought to prolong endurance exercise via increases in fat oxidation through the mobilization of free fatty acids from adipose tissue or intramuscular fat stores. Using fat as the primary fuel source slows glycogen depletion and delays fatigue.

How To Take Caffeine Before Exercise:

  • According to the International Society of Sports Nutrition guidelines, caffeine effectively enhances performance in endurance-trained athletes when consumed in low-to-moderate doses (~3-6 mg/kg or roughly 200-400 mg for a 150 lb person) approximately 60 minutes before exercise, but does not result in further performance benefits when consumed in higher dosages (≥ 9 mg/kg).
  • Additionally, for prolonged exercise sessions lasting longer than 2-3 hours, smaller additional doses of caffeine may be repeated during the exercise bout, in the amount of 1-2 mg/kg (Smith-Ryan, Antonio 2013).  This amount is easily obtained in caffeinated sports drinks, gels or chews and may be preferable for endurance athletes competing in events lasting several hours.

What Does The Research Say About Caffeine?

Improvements in endurance performance following caffeine intake have been observed consistently in events lasting 15-120 minutes at an intensity of 70-75% VO2max, in time trial performances (simulating competitive events such as the 10k), and in time to exhaustion tasks in cycling and running. 

Pasman and colleagues examined the effect of varying quantities of caffeine on endurance performance.

Nine aerobically trained cyclists performed six rides to exhaustion at approximately 80% maximal power output.

Subjects consumed four treatments on separate occasions: placebo, 5, 9, and 13 mg/kg of caffeine in capsule form.

Results were conclusive in that all three caffeine treatments significantly increased endurance performance as compared to placebo.

Moreover, there was no statistical difference between caffeine trials.

Therefore, increases in performance were comparable for both the moderate dose of 5 mg/kg as well as the high dose of 13 mg/kg.

The average increase in performance time was 27% for all three caffeine treatments.

Results from that paper indicated no statistical advantage for consuming an absolute dose of 300 mg, as opposed to 200 mg.

However, the 200 mg dose did result in significant improvements in performance, as compared to 100 mg, and 100 mg was at no point statistically different or more advantageous for performance than placebo.

In an earlier study published by Graham and Spriet, seven elite runners performed a total of four trials, two cycling to exhaustion and two running to exhaustion at approximately 85% VO2max.

Times for running and cycling were both significantly improved, running increased from ~49 min for placebo to 71 min for 9 mg/kg of caffeine, cycling increased from ~39 min for placebo to ~59 min for 9 mg/kg of caffeine.

Results were comparable in a separate 1992 Spriet et al. publication.

In a crossover design eight subjects consumed both a placebo and caffeine treatment at 9 mg/kg and 60 minutes later cycled to exhaustion at ~80% VO2max. Once again, following caffeine supplementation times to exhaustion were significantly increased.

Results indicated subjects were able to cycle for 96 min during the caffeine trial, as compared to 75 min for placebo.

Recently McNaughton et al. reported the effects of a moderate dose of caffeine (6 mg/kg) on 1-hour time trial performance.

This investigation is unique to the research because, while continuous, the protocol also included a number of hill simulations to best represent the maximal work undertaken by a cyclist during daily training.

The caffeine condition resulted in the cyclists riding significantly further during the hour-long time trial, as compared to placebo and control. In fact, time trial performance was improved 4-5% by the caffeine treatment over the other two treatments.

The use of caffeine in anhydrous form, as compared to a cup of caffeinated coffee, seems to be of greater benefit for the purpose of enhancing endurance performance.

In addition, a low-to-moderate dose of caffeine between 3 and 6 mg/kg appears to be sufficient for enhancing performance in a maximal sustained endurance effort.

Is Supplementing With Caffeine Safe? Are there any side effects?

In short, YES and yes!

Despite popular belief, current research does not support the notion of caffeine-induced dehydration during exercise, or any change in fluid balance that could be detrimental to performance (Goldstein et al. 2010). 

High doses of caffeine (≥ 9 mg/kg body weight) have been associated with increased anxiety, palpitations, restlessness, headache, difficulty sleeping, and gastrointestinal distress, particularly in non-habituated users.

Caffeine toxicity is extremely rare, due to the amount that would be required to reach lethal limits in the blood (5-10 grams, or roughly the equivalent of drinking 75 cups of strong brewed coffee over a short time period).

The Bottom Line On Caffeine:

Caffeine has many potential benefits for endurance performance and appears to be ergogenic in most exercise situations. 

Improved energy, increased concentration, and alertness are the primary reasons for caffeine consumption. 

Athletes and trained individuals seem to benefit more than untrained individuals, at least as far as performance is concerned. 

Side effects and adverse events are generally mild and occur more often in naive users, with dosages ≥ 9 mg/kg known to increase their incidence. 

Be sure to read labels and know how much caffeine is in the products you are taking, particularly if you consume more than one type of caffeine-containing product daily (thermogenic, pre-workout, caffeinated beverages, etc.). 

As with most interventions, individual results may vary.


Anderson, D.E. (2013). Caffeine. In A.E. Smith-Ryan & J.A. Antonio (Eds.), Sports nutrition & performance enhancing supplements (pp. 201-223). Ronkonkoma, NY: Linus Learning.

Astorino, T. A., & Roberson, D. W. (2010). Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: a systematic review. J Strength Cond Res, 24(1), 257-265. doi: 10.1519/JSC.0b013e3181c1f88a

Astrup, A., Toubro, S., Cannon, S., Hein, P., Breum, L., & Madsen, J. (1990). Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers. Am J Clin Nutr, 51(5), 759-767.

Diepvens, K., Westerterp, K. R., & Westerterp-Plantenga, M. S. (2007). Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green tea. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology292(1), R77-R85.

Goldstein, E. R., Ziegenfuss, T., Kalman, D., Kreider, R., Campbell, B., Wilborn, C., . . . Antonio, J. (2010). International society of sports nutrition position stand: caffeine and performance. J Int Soc Sports Nutr, 7(1), 5. doi: 10.1186/1550-2783-7-5

Graham, T. E. (2001). Caffeine and exercise: metabolism, endurance and performance. Sports Med, 31(11), 785-807.

Jeukendrup, A. E., & Randell, R. (2011). Fat burners: nutrition supplements that increase fat metabolism. Obesity reviews12(10), 841-851.

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