Or you might be sipping on a latte while you browse the internet, had a diet soda with lunch, or ingested it in a half-dozen other ways. From tea to chocolate, cocoa, colas, and a lot of over-the-counter medicines, caffeine is hard to avoid. Maybe that’s why 90% of Americans consume an average 200 mg of coffee a day—though 10% of the population consumes closer to 1000mg. And according to Johns Hopkins, half of all American adults consume 300 mg or more every day, making it far and above the most popular perfectly legal, socially acceptable drug in the country.
And ever since laboratory studies in the 1970s suggested that caffeine was not just a mild stimulant, but could actually increase endurance performance, athletes have been the drug’s biggest fan. Happily for elite competitors, it’s even legal under Olympic Committee rules. (Unsurprisingly, the journal Applied Physiology, Nutrition, and Metabolism found that over two thirds of the close to 21,000 athletes they studied had caffeine in their bloodstream.)
How does it work? From your first sip, caffeine is already entering your blood stream through the lining of your mouth, throat and stomach. It only takes about 45 minutes for 99% of the caffeine to be absorbed, but your adrenaline output increases almost immediately. This extra adrenaline floating around in your system stimulates the release of free fatty acids into your blood—and that’s the extra fat your muscles use in the early stages of endurance exercise. Which means you put off using your muscles’ glycogen, delaying the inevitable, hard-to-overcome fatigue when you use it all up. Science has found the effects are dramatic, but may even go beyond your muscles.
A study in the Journal of Applied Physiology gently tortured team sports players by sending them through a grueling workout consisting of intense sprinting and then long runs. A capsule of caffeine about an hour beforehand had those runners performing 16% better. Soccer players in a British Journal of Sports Medicine study dribbled, headed and kicked the ball more accurately with caffeine in their systems. Coventry University researchers asked 13 hale and hearty young men to perform a weight-training session to exhaustion; the athletes who had caffeine? They put more work and effort into their routine, completing a significantly greater number of repetitions, and reported being less tired throughout the exercise routine. But perhaps most interestingly, they expressed satisfaction with their workout and enthusiasm for doing it again soon.
So beyond affecting your muscles and muscle fatigue, caffeine also seems to have a remarkable effect on your central nervous system as well as the bits of your brain that control mood, alertness and fine motor control.
It’s tempting to go rushing off to the coffee shop to reap the many and varied athletic rewards of caffeine, but hold on just a moment—caffeine also has its drawbacks. To begin with, even science doesn’t know how big or small a dose offers reliable results. It definitely has a lot to do with your tolerance, size, and gender. But when you’re experimenting you’ll find that too big a dose adds those unpleasant side effects like the jitters, a touch of anxiety, sometimes nausea, and always heightened blood pressure, not to mention an urgent rush to the bathroom. And then all your experimentation could have you lying in bed that night staring up at the ceiling, lamenting all the coffee you drank and wondering if you’ll ever sleep again. That’s definitely a problem, seeing as how sleep is just as important to your health and happiness as regular exercise, and much more pleasant.
There’s also the fact that it hasn’t been determined if caffeine will work the same way for exercisers who regularly ingest caffeine in all its forms. If you’re drinking coffee and soda and tea all day, what kind of effect will adding an extra cup right before your workout have? Or will exercisers who rarely if ever drink the stuff outside of the gym reap all the rewards? As with any drug, your body builds up a tolerance—but researchers haven’t yet decided just how much effect that tolerance could have on the exercise benefits you’re looking for. And then there’s the physical addictiveness of caffeine, the unpleasant, headachy withdrawal when you get yourself hooked, and the undeniable fact that while black coffee is a non-calorie drink, heaping milk and sugar and syrups into it is a little counterintuitive.
So it’s not a miracle drug, sadly. But there’s no doubt that if you’re smart about how much you drink, careful about your caffeine delivery system (for instance, opting for green tea without sugar over a frappuccino with extra whipped cream), and make sure there’s a cut-off time to make sleeping an actual possibility, caffeine can be a real aid in getting the most out of your workouts.