Positive effects of caffeine on athletic performance


May 30, 2019

By Hubert Cormier, Nutritionist and Doctor of Nutrition

In the world of sport, it is not uncommon to see athletes consuming coffee, caffeinated beverages or pre-workout supplements before training or competition. In fact, some studies have demonstrated caffeine’s benefits on sports performance. But does caffeine improve performance for all athletes? And how exactly does it work? Are there any side effects? What are the specific recommendations? Here is an overview about caffeine’s impact on athletes!

Positive effects of caffeine on athletic performance

According to several scientific studies, coffee and caffeine have a performance-enhancing effect on muscular activity, which results in improved athletic performance. This effect is observed, in particular, during long endurance exercises such as running.

According to a study of cyclists, they achieved better performance in terms of speed and power after a caffeine dose of 5 milligrams (mg) per kilogram (kg) of body weight taken 60 minutes before exercise, compared to cyclists who had not consumed it. The results of 12 different studies on the subject also show that athletic performance improves by an average of 3% with caffeine intake and that reflexes, motor coordination and concentration are also optimized.

How does caffeine work? 

Caffeine acts primarily on the nervous system. Among other things, caffeine competes with adenosine, stimulates adrenaline secretion, increases the cellular secretion of ions and reduces feelings of pain and fatigue during exertion.

“Did you know that between 1984 and 2004, Olympians with a high concentration of caffeine in their blood (higher than 12 μg/ml of blood (or the equivalent of about 8 shots of espresso in a few hours) were banned from Olympic events by the World Anti-Doping Agency?”

What about dehydration?

Have you ever heard that coffee dehydrates? Should it be avoided during intense physical activity that causes sweating? After all, we do want to maintain our fluids, at all costs. Well, this myth is simply not true. Caffeine contained in coffee and tea has no diuretic effect when consumption remains under 225 mg of caffeine per day. In addition, even with consumption greater than 225 mg, the amount of liquid ingested remains higher than the amount lost in the urine. Thus, whether consumed in small or large quantities, drinking coffee does not cause dehydration!

Possible side effects

  • Drinking coffee before exercise is not recommended for everyone. In fact, some individuals will react very positively to the effects of caffeine while others will be more sensitive. Some suffer from insomnia before competitions or notice an increase in the urge to urinate, while others experience palpitations, nausea, headaches or even anxiety;
  • Also, for those already suffering from gastric reflux, ingesting caffeine during physical activity can greatly exacerbate the symptoms;
  • Lastly, one of the most frequently experienced side effects is diarrhea, which in most cases is accompanied by abdominal cramps. This can occur both during and after physical activity.
The best way to find out if caffeine is right for you is to experiment with it and note its effects, because everybody reacts to it differently. And what about your genetics?

Course_Cafe_HubertStJean_BeCoffeePhoto: Cafe Hubert Saint-Jean

Individual tolerance

Individual tolerance depends on several factors, including genetics (the CYP1A2 gene alone is responsible for 95% of caffeine metabolism), your gender, age, the time of day, your caffeine consumption habits, whether you use of alcohol and tobacco, oral contraceptives or other medications, whether you are pregnant, breastfeeding, or experiencing a menstrual cycle, your physical fitness, and the method of administration.

In short, you may experience some or more benefits or side effects depending on all of these factors. For example, those carrying a mutation of the CYP1A2 gene (genotype AA) may gain an advantage in sports competitions. A 2018 scientific study published in the journal Medicine & Science in Sports & Exercise reports that ingesting 2 to 4 mg of caffeine per kg of body weight improved performance during a 10 km cycling trip (4.8% faster at 2 mg/kg and 6.8% at 4 mg/kg), whereas a neutral effect was reported for AC genotypes, an performance actually decreased (13.7% slower) for those in the CC group.


According to science, caffeine takes about 15 minutes to enter the bloodstream after being ingested. However, its full effects reach their peak about one hour after consumption. Therefore, a dose of 3 to 9 mg of caffeine per kg of body weight is recommended approximately one hour before exercise, for optimal results. But be careful! Caffeine’s effects can still be felt 3 to 4 hours after consuming it and Health Canada recommends not exceeding 400 mg of caffeine per day.

Enjoy your coffee!