How to Use Caffeine to Boost Your Workouts

Credit: Jacqueline Harriet / Getty Images

Athletes love caffeine for a performance edge — it improves alertness and concentration, spikes adrenaline, aids muscle function, and blocks certain brain receptors, which makes exercise feel easier. 

But because you can build up a tolerance to the stimulant, many athletes give it up for days or a week leading up to a competition, thinking they need a “caffeine detox” in order to get the maximum desired effects from a pre-event dose. While there is some evidence to support this idea, a new study suggests abstaining is pointless — that even habitual caffeine users will score that boost on game day. However, it also opens up even more questions about America’s favorite drug.

To test the caffeine detox theory, Brazilian physiologists asked 40 male endurance cyclists how much coffee, tea, soda, energy drinks, and other caffeinated drinks and foods they consumed on most days. Using preset nutritional tables to estimate the caffeine content in these foods and beverages, they broke the men into three groups: low-caffeine consumers (2 to 101 milligrams per day), moderate-caffeine consumers (104 to 183 milligrams per day), and high-caffeine consumers (190 to 583 milligrams per day).

Next, the men hit the bikes for three separate 30-minute time trials. An hour before one session, they took a pill containing about 400 milligrams of pure caffeine. Before another, they popped a placebo pill. For the final time trial, the men took nothing. No shocker, after getting the jolt of caffeine, the cyclists pedaled 2.4 percent faster on average than when they took the placebo, and 3.3 percent faster than when they didn’t take a pill.

Here’s what wasn’t expected: The cyclists' regular caffeine intake didn’t matter. The high-caffeine group got the same performance edge from the pre-trial caffeine as the guys who rarely or never used caffeine in their daily lives.

“This was surprising considering that low and high habitual caffeine consumers may show different responses to acute caffeine supplementation on mood and cognition,” says study author Bruno Gualano, a physiology professor at the University of São Paulo. “Based on our findings, however, high-habitual caffeine consumption may not be sufficient to negate the effects of acute caffeine supplementation on physical performance, as previously assumed." In other words, you can chug a cold brew before a 5k and get a performance boost, even if your body is used to getting mega doses of coffee every morning. 

So, does this research make the case closed? Not necessarily, says Anthony Almada, a caffeine researcher and co-founder of the International Society of Sports Nutrition. “This study adds a new chapter to the book of caffeine, but there are some big weaknesses in it,” Almada says. “For one, when the researchers determined how much caffeine the cyclists took in, they assumed that one cup of coffee was 4 ounces versus, say, 16 ounces. That is a huge, error-prone assumption.”

Beyond cup size, the amount of caffeine in one coffee can differ considerably from another of the same size, depending on the beans, brewing method, grind, and other factors. “The researchers used nutritional tables to assess these guys’ caffeine consumption, but those amounts may be very different from what they actually took in,” Almada says. As proof, he points to a 2003 University of Florida study in which researchers went to the same Starbucks on six consecutive days, ordered the same grande coffee each time, and tested its caffeine content. One day it had 564 milligrams of caffeine, another day it contained 259 milligrams — over a twofold difference. “Caffeine is the only drug we consume in large quantities that we have no idea how much of it we’re really getting,” Almada says.

A second major weakness, which the authors acknowledge in their paper, is they didn’t measure blood caffeine concentrations. While caffeine has been shown to peak in the blood 40 to 60 minutes after consumption, other studies suggest it can take up to three hours, says Almada. “Everyone metabolizes caffeine at different rates and will show different rates of blood rise,” he explains. “They also didn’t measure the cyclists’ biological responses to caffeine, most significantly the release of adrenaline into the blood.”

Finally, because the cyclists got 400 milligrams of straight caffeine, the performance-boosting effects may have been more significant than if they’d consumed coffee or tea. Therefore, these results may not apply to those who sip their caffeine rather than taking it in pill form. “Past studies have shown that the adrenaline response is blunted when caffeine is delivered via coffee and tea because the other ingredients stymie the stimulant effect,” Alamada says. “That’s why, when you take a 5-Hour Energy, you almost feel like you’re on meth. But with coffee or tea, you don’t typically feel that. Plus, we don’t typically slam coffee; we sip it slowly, so the caffeine trickles in.”

Given all these variables and unknowns, the main takeaway, says Almada, is that everyone responds to caffeine differently, so some athletes may not need a detox before an event while others might benefit from abstaining from caffeine. The best way to know what works best for you is to run your own experiment. “I always say, ‘Test, don’t guess,’ ” Almada says. “If you have a competition coming up, sometime during your training, try abstaining for a period of time before consuming caffeine. Then measure your time and performance. Another time, after not abstaining, track your performance, and compare the two results.”

And it's important to actually measure your results versus relying just on how you feel while exercising in both circumstances. “Perceived exertion may not translate to greater performance,” Almada says. “After caffeine, your brain might say, 'This is easier,’ but it doesn’t mean you’re performing any better.” He compares it to being eager to get to a destination, making the drive there seem longer than the drive home, even though both drives are the exact same distance. If you find you actually do perform better with or without a caffeine detox, take that approach leading up to a big event.