How Does Caffeine Affect Athletic Performance?

As Registered Dietitians, we love talking about caffeine. Caffeine is often what people reach for first thing in the morning to get a kickstart to their morning and we do too! As a staple in most of our diets, we often get asked about the role of caffeine and athletic performance. You might have noticed an extra spark of energy during your workout after drinking your morning coffee and we are going to dive into the effect of caffeine on athletic performance in this blog.

Coffee is one of the most common sources of caffeine consumed

What Does Caffeine Do to the Body?

You have probably heard this at some point – caffeine is a stimulant. But do you know what this means besides making you feel alert? Caffeine acts as a stimulant for the body by increasing your circulation, making your brain, nervous system, and basically, everything in your body get more blood, which means more oxygen. This increased circulation is what helps you feel more alert, awake, and energized.

Caffeine has an average half-life of 5 hours. This means that caffeine will be circulating in your system for an average of 10 hours with its highest levels about 3-5 hours after. Caffeine will begin to kick in around 15-60 minutes after ingesting. Although it may be at lower levels after the half-life mark, caffeine is still present in your bloodstream after the half-life and can make a difference in your day. This is why caffeine is often not recommended in the afternoon or later in the day.

Benefits of Caffeine

The benefits of caffeine rely on the dose. In moderate amounts (50-200 mg) caffeine is shown to have beneficial effects. This comes out to 3-5 mg/kg for most people. Here are some of the benefits of caffeine

  • Increased attention span 
  • Better energy 
  • Higher alertness 
  • Increasing time to exhaustion 
  • Improving power 

Though beneficial for performance and your energy outside of sport, consuming more than 200mg per day can have negative side effects. You may feel side effects such as restlessness, anxiety, and increased heart rate with overconsumption of caffeine.

When Should You Use Caffeine?

Caffeine is common in all cultures around the world and you can find it in food and supplements all across the world. Most of us rely on our cup of coffee to wake up in the morning (who doesn’t love a latte right!?. Many athletes wonder if their daily cup of coffee hurts or helps their athletic performance. Research has been done to see if the benefits to athletic performance would still be present when it is habitually used outside of performance. Ultimately, the answer is it depends on the individual. 

Caffeine is a great tool that you can utilize and experiment with around training to help enhance performance. We recommend ensuring you have a good fueling foundation prior to experimenting with caffeine.

Once good fueling habits have been established, start small! We recommend a low to moderate dose (50-150mg) 15-60 minutes before training to see how you respond to it. If you are interested in exploring the benefits, you may also want to use it only around when you are performing (training, games, etc.) and decrease your use of caffeine daily. 

Research has also shown that the greater the dose does not equal greater performance in some individuals. Most benefits level out at 3-5 mg/kg of body weight. This means that a mega dosage that puts you over this amount won’t provide performance benefits and might be more detrimental to your health. The maximum daily dose of caffeine is 400 mg – which is almost as much as some energy drinks contain! We recommend that you work with a health professional to get your timing and intake down so you can see the benefits you want. 

When to NOT Use Caffeine

Even though caffeine is great and it makes us feel a lot better, it is not a fix-all. It does NOT make up for a poor fueling foundation.

Unfortunately, we see many athletes use it as a bandaid for a poor diet. Without proper fueling surrounding a workout or throughout the day, caffeine may make you feel alert for a couple of hours, but you will crash much harder than you would if you were staying fueled. 

I see clients all the time who rely on their energy drinks and have to get some caffeine in to avoid taking naps in the early afternoon. Try a snack! Making a snack or having a good breakfast in the morning may give you the energy boost you need and then you can truly focus on using caffeine and a booster in your daily routine. 

Be careful of energy drinks – they can contain high amounts of caffeine (even 300+ mg) and other unwanted substances

Are There Regulations Regarding Caffeine?

Caffeine is a heavily studied supplement. Though many studies back the benefits of caffeine for performance, it is not always safe or allowed for athletes to take. An example of this is the NCAA. Caffeine is on the banned substance list by the NCAA and consuming a large dosage could lead to a positive drug test. This does not mean you cannot have any caffeine as a college athlete. You are not allowed to have a urine concentration level above 15 mcg/mL in a drug test. This often is triggered when going over 200 mg of caffeine per day.

 Having excessive amounts of caffeine can put you over the limit, and energy drinks that contain large amounts of caffeine are also not third-party tested (besides RedBull), so they may contain other banned substances as well.  

Caffeine can help with performance but it is important to not consume more than you believe your body can handle, and time it correctly. Start small and if you feel you need to increase, talk to a professional who can give you more insight on what you need. 


If you couldn’t tell, we are not anti-caffeine! Caffeine can be used very well when it comes to performance and regular life. However, it cannot be relied on in place for food or sleep. You need to fulfill your basic needs before you rely on supplements to do that for you. 

If you have more questions on caffeine or how to fuel for energy throughout the day, apply for 1:1 coaching! We would love to help you meet your goals. 



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