Caffeine is a performance-enhancing drug that's legal, cheap, and easy to get: chances are you had some this morning. More importantly, it actually does make you better at sports, which is more than you can say for a lot of supplements marketed to athletes. You just have to know how to use it strategically.
Illustration by Sam Woolley.
What Caffeine Does
Caffeine is a multi-talented molecule that strolls through the body messing with just about everything, but its trademark move is maintaining alertness in the brain. There, it blocks adenosine, a naturally occurring chemical that slows down other brain signals when we need to rest and sleep. With the brakes off, we feel less fatigue. It's easier to focus, and exercise doesn't feel as tiring.
In endurance events -- like triathlons, marathons, and cycling races -- caffeine provides a serious performance boost. In experiments that mimic races, caffeine took an average of 3% off of athletes' finish times. In some cases, the effect was as large as 17 per cent.
Three per cent is about two minutes an hour. How would you like to shave a minute off your 5K time, or seven minutes off a four-hour marathon, just by choosing the right breakfast? Yeah, me too.
That explains why caffeine is in so many products meant for runners, like energy gels. Most athletes use it one way or another, including 73 per cent in a study published in Applied Physiology, Nutrition, and Metabolism. The highest doses were in triathletes.
Research on other types of exercise doesn't show consistent benefits, however. The International Society of Sports Nutrition writes in a position paper that we don't know enough to say if caffeine helps with strength and power sports (like weightlifting or isolated short sprints), but that it does help with sports that involve repeated sprints over time, like soccer.
Besides the brain chemistry, caffeine has other effects in the body, but researchers keep going back and forth on which of these, if any, affect exercise performance. According to Nutrition and Enhanced Sports Performance, caffeine makes our bodies burn fat rather than glycogen (stored carbohydrates), but this might not make a big difference in athletics. Likewise caffeine's effect on muscle contraction: it increases the amount of calcium available to the muscles, but doesn't overall make you stronger.
One thing caffeine doesn't do is dehydrate you. It can slightly increase the amount you pee, if you take a huge dose and aren't used to it, but the amount in a typical cup of coffee isn't enough to trigger this. That slight effect doesn't apply during exercise, though: even large doses of caffeine don't dehydrate you during exercise.
How to Get Your Buzz
Most of you are probably used to coffee with breakfast, and sure, you could just add that to your pre-race breakfast. It won't hurt and might help. (The hot liquid will also help you poo if that's high on your morning to-do list.) But to use caffeine strategically, you'll want to carefully consider all the variables: what source of caffeine, how much, and when.
Coffee might not be the best way to get your caffeine, although the research isn't clear on this. One study in the Journal of Applied Physiology found that coffee didn't have as strong an effect as caffeine pills. They figured there must be something in coffee that inhibits caffeine. But a later study in the International Journal of Sports Nutrition and Exercise Metabolism combined caffeine pills with decaf coffee and couldn't find any such effect. Without better evidence, the best approach may be to experiment with both. If you don't get much of a boost from coffee, try an equivalent amount of No-Doz.
To get the exercise benefits, you'll want between 3 and 6 milligrams of caffeine for every kilogram you weigh. Some sources, including this review from the American College of Sports Medicine, say up to 9 mg/kg is effective. (Here's a calculator to convert pounds to kilograms.) If you weigh 68kg, that means you want between 210 and 630 milligrams of caffeine. The same range for a 90kg person is 270-810 milligrams.
On the lower end, you can get the right amount with a tall Starbucks coffee (260mg) or get most of the way there with a No-Doz (200mg in the "max strength" formula). Here's a handy chart:
The numbers above are approximate where they apply to brewed beverages, like coffee and tea: the caffeine content depends on the type of bean or leaf, and the brewing time and technique.
If you use gels or similar sports snacks while you exercise, it's important to know that some have caffeine and some don't. In many brands, the difference is by flavour: some of Gu's gels have no caffeine, some have 20mg, and the coffee-flavored ones have double that. Whether you're trying to get wired or trying to avoid caffeine, it's always good to be aware of what you get when you suck down the contents of that shiny packet. That's especially true in races, where you might grab a random flavour as you cruise by a water stop. If the caffeine amount is important to you, do your research ahead of time on which flavours are which, and consider bringing your own so you know what you're getting.
You could use caffeine every day, but you'll quickly build up a tolerance to it. The tolerance will dull some of caffeine's effects, but not everything. For example, habitual coffee drinkers don't get the increased blood pressure or heart rate that a newbie would. Thankfully, if you're relying on caffeine to help you run faster in a race, you'll still get a benefit even if it's your hundredth day in a row of chugging coffee in the morning. But for the best results, you may want to go off caffeine for a week or more before an important race.
When the big day comes, the International Society for Sports Nutrition recommends taking a big hit of caffeine one hour before your event starts. Caffeine begins to circulate in your blood after about 15 minutes if you take it on an empty stomach, or longer (45 minutes or more) if you have it with food. (The delay is similar to what happens when you have alcohol with food.)
Once it's in your system, caffeine sticks around a long time. Its half life is around five hours, meaning that you've only managed to clear half of it out of your body by then. The total time it takes to leave your system depends on how much you started with: the bigger the dose, the longer you'll feel the effects.
Your liver is responsible for breaking down caffeine so that the kidneys can excrete it. The liver enzyme that has this job is a cytochrome known as CYP1A2. It does its job faster when you exercise, or smoke cigarettes, or eat broccoli. Alcohol has the opposite effect, keeping the caffeine in your body longer. Some people have more efficient versions of this enzyme than others, making caffeine metabolism a very individual thing.
Make a Plan for Race Day
Everyone's response to caffeine is a little different -- your liver enzymes, your level of tolerance, and probably a bunch of still-unknown factors come into play. So no matter what the research says, the smart thing to do is experiment on yourself before your big race.
"Nothing new, only tried and true" is the rule for important events, like the marathon you've been training for all year. That includes your caffeine plan. If you don't usually drink four cups of coffee in the morning, don't try it for the first time on race day! You don't want jitters or badly-timed bathroom breaks to ruin what could have been a great experience.
If you want to abstain from caffeine before the race, make sure you practice that, too, perhaps abstaining for a week before one of your longer training runs. And make sure you've tried out the method you plan to use, whether that's a morning No-Doz, a coffee, or a series of caffeinated gels that you down every few miles.