If there’s one thing I know about endurance athletes, it’s that we love our caffeine. We love our coffee in the morning, sports nutrition products filled with caffeine to get through tough workouts and races, and a luscious hit of dark chocolate at night. Many of us see caffeine as part of our internal regulation to keep us happy, alert, and running on all cylinders. After all, the very nature of our sport requires us to wake up early in order to jump into a cold pool, pedal on the trainer, or run with a headlamp before the rest of the world gets going. Who wouldn’t need a pick-me-up at zero-dark-thirty? 

Caffeine might be as essential to the triathlete’s training regimen as swim goggles or a bike. It’s the most widely-consumed stimulant throughout the world, found in substances such as coffee, tea, energy drinks, chocolate, and soda. But could that constant daily exposure to caffeine be hurting us on race day?

Many of us know the benefits of caffeine as an ergogenic (work-producing) aid to lessen the perception of fatigue and help with sustained intensity for longer durations. However, if you are a regular caffeine user in your daily life, you’ve probably been warned that your tolerance reduces its race-day stimulation. A new study by Carvalho et al. (2022) set out to determine if habitual caffeine consumption impacted the overall potential benefits of caffeine for both trained and untrained men and women in differing sport types (endurance, power, and strength). 

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How caffeine works during exercise

Caffeine is an effective stimulant because it is close in structure to the compound adenosine, which makes you tired. This similar structure makes caffeine an adenosine antagonist – in other words, caffeine blocks adenosine from attaching to the synapses within the brain that signals sleepiness. Simultaneously, there is an indirect effect on the release of other “feel good” neurotransmitters, including norepinephrine, dopamine, serotonin, glutamate, and perhaps neuropeptides. Because the brain hasn’t gotten the message to feel tired, and because it has gotten the message to feel excited, humans feel more refreshed and focused than before we made that Starbucks run.  

Within an exercise bout, caffeine has been supported by moderate to high-quality evidence to have acute benefits such as positive work-producing impacts on muscle endurance, muscle strength, and aerobic endurance.  However, certain studies suggest that habitual caffeine users negate some of the positive benefits to exercise that occur with caffeine use over time.  The most recent study aimed to determine if that was the case by quantifying the amount of research published on habitual caffeine consumption. 

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Does consuming caffeine daily reduce its effectiveness on race day?

Studies with an intervention had to include acute caffeine supplements (of any kind) before an exercise task compared to a control group without caffeine supplementation while doing the same exercise. Finally, outcomes of the exercise task needed to be evaluated as changes in exercise performance or capacity. After screening, 60 caffeine studies met these requirements and were included in the meta-analysis, which included 1137 participants—84% were male, 718 were trained, and 400 were untrained.  

After the statistical analysis, the results suggested a small positive overall effect of caffeine supplementation on exercise outcomes of endurance, power, and strength regardless of regular caffeine consumption, sex, or level of training (trained vs. untrained).  In addition, this positive effect only occurred when the acute dose was under 6mg/kg body mass, but not over this amount. This is consistent with previous literature which suggests quantities of 2-6mg/kg body weight are appropriate to produce an ergogenic effect on performance in most athletes.

Additionally, caffeine had this positive work-producing effect regardless of whether the acute dose in the study was higher or lower than the participants’ regular daily dose administered caffeine or if the research protocol included a withdrawal period before entering the study. One limitation to these findings was that only 24% (60/246 studies) reported their participant’s mean habitual caffeine intake, reducing the impact of these results. Therefore, many studies didn’t take this into account and could not be used for the final analysis. 

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Do I need to cut back on caffeine before race day?

While many coaches suggest a caffeine withdrawal period before a big race or endurance event, the results of this study do not support caffeine withdrawal as a necessary or effective method for producing an ergogenic effect during a race. Regardless of habitual caffeine intake or the acute dose ingested, an ergogenic effect was reported so long as that acute dose was under 6mg/kg body mass. As a handy reference, we’ve included a table below of common caffeinated beverages, sourced from the Harvard School of Public Health.

Beverage	Caffeine content
Average 8-ounce coffee	95 mg
Single-shot espresso (1.5oz.)	65 mg
Black tea	47 mg
Green tea	28 mg
Cola (12oz.)	40 mg
Average energy drink (16oz.)	170 mg

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Conclusions

The long and short of the study is good news for many athletes who are daily coffee drinkers. Anyone who has experienced the side effects of caffeine withdrawal – headaches, drowsiness, impaired concentration, depressed mood, anxiety, and irritability – should be letting out a small cheer right now. The taper period can be hard enough as it is, so there’s no need to add caffeine withdrawal on top of that. 

To get the most out of your caffeine consumption, it would be a good idea for you to experiment with caffeine in doses of 2-6 mg/kg body weight in training to determine how it impacts you personally. Some athletes feel extra jittery on race day, and this may or may not be a good thing to nail your “A” race. It has been suggested that not all athletes have the same reaction to caffeine, and that genotype may play a role in that response. However, until you know your genotype, working with a sports dietitian and tracking your individual response with varying caffeine levels within the proposed range can help identify a caffeine strategy that offers the most potential performance benefits.

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