Health

The Performance-Enhancing Power of Caffeine

The world's most widely used drug boasts some powerful benefits for runners.

Caffeine is the most widely used drug in the world. In fact, according to the International Coffee Organization (ICO), the world pours about 1.4 billion cups of joe a day. Despite the negative connotations of the word drug, however, caffeine is by and large a benign and even beneficial substance for humans. “Acute caffeine consumption”—the scientific term for drinking a cup of coffee—has been shown to enhance mental alertness and mood state and is also known to boost athletic performance.  “Chronic caffeine consumption”—the scientific term for drinking a cup of coffee every morning—has been associated with a reduced risk for a number of disorders including type 2 diabetes, gallstones, and Parkinson’s disease. Not too shabby.

While moderate caffeine consumption is deemed best, even fairly high levels of regular caffeine use are not associated with any significant health risks. That said, it certainly is possible to consume too much caffeine, and some caffeine-sensitive individuals react poorly to even small amounts of the stimulant. But the bottom line is that caffeine can be a boon to a runner before, during, and after a workout or race.

Caffeine Before Exercise

Above shot of coffee in mug with fresh bubbles

Photo: Nathan Dumlao / Unsplash

Research has shown that pre-exercise caffeine enhances performance in sprints, in all-out efforts lasting four to five minutes, and in prolonged endurance activities. In shorter events, caffeine apparently increases muscle recruitment, which ultimately boosts performance. In longer events, it delays fatigue by reducing the athlete’s perception of effort. Caffeine does this by increasing the concentration of hormone-like substances in the brain called ß-endorphins during exercise. The endorphins affect mood state, reduce the perception of pain, and create a sense of well-being.

Three important questions about caffeine use before exercise have not yet been definitively answered by science:

1) Is it performance-enhancing for every athlete, or just some?
2) Is the performance boost associated with pre-exercise caffeine intake greatest in individuals who normally don’t use it (or have taken a break from it)?
3) What is the optimal dosage, and does this also vary between individuals?

In recent years, there has been some research indicating that individuals carrying certain variations of the CYP1A2 gene might not gain a performance benefit from pre-exercise caffeine intake, and in some cases may even be slowed down by it. The latest evidence, however, suggests that the number of “non-responders” within this subpopulation (which itself represents only a fraction of the overall athlete population) is quite small. In the absence of direct evidence to the contrary, therefore, it’s safe to assume that caffeine is performance-enhancing for you.

Genetics aside, another, more controllable factor that may affect whether or how much pre-exercise caffeine intake elevates your running performance is the role of caffeine in your daily life. Science has gone back and forth on this question, with the most recent research suggesting that caffeine is most effective in athletes who do not habitually drink coffee or consume other caffeine sources, or who have at least taken a break from caffeine prior to using it as an ergogenic aid. A study led by Juan Del Coso of Camilo José Cela University in Spain and published in PLoS One in 2019 compared cycling performance in subjects during two, 20-day periods, one with daily caffeine intake and the other without. They found that the performance boost resulting from caffeine all but disappeared after six days. It’s important to note that the subjects chosen for this study were all light caffeine users normally, and further research is still needed to nail down whether habitual caffeine users need to lay off the coffee for a while to benefit from caffeine pre-exercise ingestion. In the meantime, it’s best to assume you do. Speaking from personal experience, I can say I certainly feel the effects of caffeine more strongly after several days without it. 

As for dosage, a recent, comprehensive scientific review and meta-analysis by New Zealand researchers reported that doses in the range of 3 to 6 grams of caffeine per kilogram of body weight yield maximum performance benefits in a majority of athletes, with 6 g/kg seldom offering any more of a boost than 3 g/kg, although some individuals do better at the lower end of this range and others at the higher end. Lower doses (in the range of 200 mg) are hit-or-miss, aiding some athletes and not others.

You may want to try a little informal experimentation to find out whether caffeine aids your running, and how much is optimal for you. One way to do this is to choose a harder workout type (hill repetitions, tempo runs, speed intervals) that you do regularly in your training and switch up your pre-workout caffeine regimen each time you repeat it. Specifically, try cycling through options ranging between 0 mg and 6 mg (or whatever upper limit you’re comfortable with) in random order. Obviously, there are a variety of factors that affect how you feel and perform in training on any given day, so you’ll need to try each option more than once to identify patterns and tease out the regimen that seems to work best.

Caffeine During Exercise

A 2008 study, conducted at the University of Birmingham in England, looked at a completely different benefit of caffeine. It studied the effect the stimulant had during exercise on exogenous carbohydrate oxidation—which is the rate at which consumed carbs are burned.

Cyclists received either a 6% glucose solution, a 6% glucose solution plus caffeine, or plain water during a two-hour indoor cycling test. The researchers found that the rate at which the consumed carbohydrates were burned was 26% higher in the cyclists receiving carbs with caffeine than in those receiving carbs without caffeine. The study’s authors concluded that caffeine may have increased the rate of glucose absorption in the intestine, providing fuel to the working muscles more quickly. The likely effect on performance is the ability to work harder for a longer period of time without becoming fatigued.

Based on these results, athletes might want to consider consuming caffeine along with a sports drink or chew on caffeine-laced gum during races or long training sessions instead of dosing up beforehand. Taking in caffeine both before and during a race or workout would be excessive and could lead to nervousness, anxiety, and stomach upset.

Caffeine After Exercise

Here we’re not talking about consuming caffeine after exercise to produce a benefit outside of the happiness found in a cozy post-run coffee, but rather how taking in caffeine before a workout may make you feel better after the workout. A 2007 study from the University of Georgia found that pre-exercise caffeine intake reduced post-exercise muscle soreness by 50%. This is another effect that is unlikely to be felt by regular caffeine users, however. So again, wean yourself off caffeine for one week before big races or an important marathon training run, dose up that morning, and expect to not only perform better but also to experience faster muscle recovery afterward.