Athletic performance: The caffeine connection

Performance booster? The pros and cons of caffeine

— By Casey Jones

Remember your first coffee? It might have felt something like a euphoric boost of energy that made you feel like you could do anything. If you’re like many others, you may have become accustomed to caffeine’s effects and drank more and more coffee to get the same effects. It may even be harming your sleep habits, leaving you weary-eyed in the morning, perpetuating a vicious cycle of caffeine consumption.

Your morning coffee, caffeinated pre-workout, and afternoon tea aren’t all bad, though. When consumed in the appropriate amounts, caffeine can be a powerful performance booster. Today we’re diving into the scientific literature to get the true picture of the pros and cons of caffeine.


After you ingest caffeine, it is absorbed by your intestines, and reaches peak levels in the body between 15 and 120 minutes, depending on how you take it (liquid, capsule, etc.). The caffeine molecules are then shuttled by the bloodstream into your liver, where the enzyme CYP1A breaks caffeine down (1).

Interestingly, depending on your genetic makeup, you may be more or less sensitive to the effects of caffeine (2). Variation in the enzymes that break down caffeine in the body (CYP1A1 and CYP1A2) can cause you to break down caffeine faster than others, making you less sensitive to its effects, or vice versa. The fact that everyone metabolizes caffeine differently means that you should listen to your body when managing your caffeine intake.

After being metabolized, caffeine acts as a blocker (or antagonist) of the adenosine receptor in the brain. Adenosine is a neurotransmitter that normally plays a role in promoting sleepiness, and suppressing arousal.  So when caffeine blocks the actions of adenosine, we feel more alert, attentive, and awake.

Caffeine can also indirectly increase dopamine levels. Dopamine is the neurotransmitter that makes us feel happiness and improves our mood.

Now that we understand why caffeine makes us feel more awake, does it benefit athletic performance?


After having a coffee, tea, or pre-workout supplement it’s almost inevitable that you feel an energy boost soon after. But does this perceived increase in energy translate to improved performance athletically? The scientific consensus points to yes.

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Caffeine results in a notable increase in anaerobic capacity, power output, and endurance capacity (1). These studies were carried out with doses of caffeine around 5 mg/kg for an individual, meaning a 175 lb individual would be given a 400 mg dose, equivalent to a large medium roast coffee at Starbucks. (3)

You don’t necessarily need a 20 oz coffee before a workout to boost performance though; a recent review also showed that lower doses of caffeine (3 mg/kg or less) can help performance in sport as well (4).

Other minor effects of caffeine include increases in adrenaline, fat burning, metabolic rate, and blood flow.


Despite caffeine’s many benefits, the more coffee you drink blunts its effects. The human body quickly adapts to the effects of caffeine, like with most drugs.

Unlike other drugs, tolerance to caffeine is “insurmountable,” meaning that drinking more coffee can’t overcome it (1).

Still, many people consume more and more caffeine to achieve the same effect, which can result in a state of dependence.

If you’ve ever tried to stop drinking caffeine for a period of time, you may be able to attest to the nasty withdrawal symptoms like headache and fatigue that go along with it. Additionally, too much caffeine can affect your sleep quality and quantity.


If you’re looking to reap the performance-enhancing benefits of caffeine, maybe you shouldn’t reach for that cup of joe every morning.

The effects of caffeine on power output, anaerobic capacity, and other athletically relevant traits fade away with caffeine tolerance. This means that the more often you drink caffeine, the less pronounced the effects will be. Therefore cycling your caffeine intake is recommended so you get the biggest workout-boosting effect.

If you want to cut back on coffee, try slowly eliminating it from your daily routine. Reduce your intake daily, even gradually substituting with decaffeinated products. Optimizing your sleep is essential to your performance as well, and may help you wean off caffeine.

If you’re used to using a pre-workout supplement, there are many caffeine-free options that can boost your performance. These supplements include ingredients like beta-alanine, creatine, and L-carnitine, which are not stimulating but can give you a boost.

So sleep right and try to only have caffeine when you really need it to get the best performance benefits possible!

Casey Jones is a master's in science student at Dalhousie University, where he studies the link between the human microbiome and pediatric Crohn’s disease in Nova Scotians.