Hoping to enhance the effect of caffeine as a performance aid, Gaudreau, who lives in San Diego, drank a cup of coffee on race day as she warmed up. Once that prerace caffeine boost hit, Gaudreau, now a nutritional therapy practitioner and strength coach, said she felt a sense of euphoria, which helped her feel focused and mentally prepared for her race. The strategy paid off. In 2010, she took first place in a regional amateur biking race called the Kenda Cup.
Caffeine is the most widely consumed psychoactive substance in the world and one of the best studied. Scientists have been looking at caffeine’s effect on athletics since the 1900s. Although there is still some disagreement as to the exact mechanism by which caffeine consumption affects exercise performance, and whether taking a break from it until game day can give you an edge, scientists agree that a cup of coffee before working out can improve performance, whether you’re playing for the NBA or just running through your neighbourhood.
However, it’s important to be aware of the potential downsides of caffeine consumption and to know how best to use it to your advantage when working out.
How much of a boost can caffeine give?
Gaudreau wasn’t imagining the effect of her prerace cup of coffee. There’s a good consensus among scientists that caffeine gives an exercising edge, whether it’s running a marathon, lifting weights or playing soccer, said Nanci Guest, a dietitian, coach and researcher at the University of Toronto who led a comprehensive review in 2021 of caffeine and exercise.
Whether consumed via coffee, a workout supplement or an energy drink, caffeine tends to improve performance by an average of 2% to 5%, said Brad Schoenfeld, a professor of exercise science at the Lehman College in the New York City borough of the Bronx and director of the school’s human performance and fitness program. Although caffeine moderately improves anaerobic activities (intense, shorter workouts), such as weightlifting, sprinting and high-intensity interval training, it appears to show the most benefit with aerobic efforts (less-intense, longer exercises), such as swimming, cycling and jogging.
For instance, a 2020 analysis of multiple studies about the effect of caffeine on rowing performance found that competitive rowers improved their time on a 2,000-meter row by about 4 seconds when using caffeine.
“It takes a lot of work to drop your 2,000-metre row, if you’ve been training for a couple of years,” said Mike Nelson, an associate professor at the Carrick Institute for Clinical Neuroscience. “But if you said, ‘Hey, just take this supplement and we can decrease your time instantly by 4 seconds,’ I’m going to take the supplement.”
This response to caffeine varies from person to person, depending on factors such as genetics, sex, hormonal activity and even diet. Some see performance improvement above 5 per cent, while others experience almost none.
“There’s fast metabolizers of caffeine and slow metabolizers of caffeine,” Nelson said.
How does it work?
Caffeine’s influence on our nervous system starts with adenosine, a neurotransmitter that binds to specific receptors and makes us feel drowsy. Caffeine binds to those same receptors, blocking the adenosine from working.
“When caffeine blocks that receptor, the result is a stimulating effect,” Guest said. This, in turn, releases other hormones such as dopamine and epinephrine, which are related to mood, focus and alertness.
Some studies have shown that caffeine also helps our muscles produce more force. Our body needs calcium to initiate muscle contractions, and caffeine helps mobilize calcium ions so they have a greater interaction with the filaments that induce muscle fiber contractions.
“Caffeine enhances the ability for muscles to contract at a greater rate and thus would conceivably create greater power,” Schoenfeld said.
Other studies show another powerful force at work: the placebo effect. If we expect caffeine to help us perform better, that may be enough. In one small study, competitive sprinters performed just as well with caffeine as they did with a placebo, as long as they had been told they ingested caffeine. When the athletes were told they had been given a placebo, they ran more slowly, even if they had actually been given caffeine.
In other studies, like the rowing paper, experts do see improvements in performance over placebos but not in measures such as oxygen consumption, heart rate or how hard the workouts felt. The human body is extremely complex, Schoenfeld said, and it’s often difficult to tease out the effect of one chemical on athletic performance.
How should you use caffeine to help your athletic performance?
Whether physical or mental, the benefits of caffeine apply to competitive athletes and those just wanting a slight improvement in their workout. One study found that caffeine improved the 5K times of well-trained runners by 11 seconds and recreational runners by 12 seconds.
“To the elite or high-level athlete, it’s going to mean a lot,” Nelson said.
Studies show that the ideal performance-enhancing dose ranges from 1.4 to 2.7 milligrams per pound of body mass (although some research shows that even lower doses can work).
For instance, an 8-ounce cup of coffee has about 100 milligrams of caffeine, although this can vary depending on the type of coffee and the method of brewing. So, two cups of coffee for a 150-pound person comes out to 1.3 milligrams per pound.
It may take some experimentation to find the right dose for you, because people metabolize caffeine differently. Whatever your ideal dosage, be sure to take it about an hour before exercise to allow time for your bloodstream to absorb the caffeine.
“The only thing I would say,” Guest said, “is that somebody who’s not really executing a lot of energy, like they’re going for a walk, they would probably want to go with a lower dose, because when you’re stimulated, you need an outlet.”
Side effects and tolerance breaks
Although caffeine can help your exercise performance, it does have some adverse effects.
“If your performance involves fine motor skills, anecdotally, those people tend to do worse,” Nelson said.
If you drink coffee late in the day to help your evening workout, you may be disrupting your sleep.
“People underestimate the value of sleep,” Guest said. Whatever performance gains that caffeine is giving you could be nullified if you are experiencing chronic sleep deprivation. Caffeine also has other side effects for some people, including nervousness, anxiety and increased blood pressure.
If caffeine does worsen your sleep, Guest recommended taking it about 8 to 12 hours before bedtime, depending how quickly your body metabolizes the chemical.
As for Gaudreau’s strategy of abstaining from caffeine to boost its performance-enhancing effects, a recent analysis of multiple studies found that habitual consumption doesn’t blunt caffeine’s performance-enhancing effects. You might experience a stronger placebo effect if you save your caffeine usage for before a competition. But Guest also cautioned that the side effects of caffeine withdrawal, such as headaches, fatigue and impaired concentration, could affect your training sessions, making you less prepared on game day.
For people who aren’t competitive athletes, the benefit of caffeine might be more about going to the gym than performing well there. After all, if your morning cup of coffee is what gets you out of bed, that might be all the performance enhancement you need.
(Hilary Achauer is a freelance writer focused on fitness, health, wellness and parenting)
This article originally appeared in The New York Times.