Caffeine is the world’s most-used drug, with around 90% of adults consuming caffeine daily. Whether it’s in your mug of coffee first thing in the morning, or your afternoon soda, the majority of us consume and (maybe even) rely on caffeine to get through the day. 

Athletes are particularly enthusiastic users of caffeine as evidence suggests that it can enhance endurance, anaerobic, strength and skill-based performance. 

A four year investigation conducted between 2004 and 2008 found that ~74% of elite athletes had used caffeine prior to, or during, a sporting event and that endurance athletes were the most prevalent users. Ten years later, this prevalence increased to ~76%

Clearly, a large majority of endurance athletes use caffeine as part of their fueling strategy for training and racing, but should all athletes be using it? 

The simple answer is ‘no’, because everyone responds differently to caffeine. 

So, before you start considering how to use caffeine before and during your training and races, let’s look at how you respond to caffeine to determine whether you should be using it as part of your strategy… 

How caffeine affects your performance

Caffeine is a stimulant and has long been known to increase our ability to focus, our perceived energy levels and our productivity, which is why it’s a staple of many people’s lives when they’re trying to perform. 

In the 1940s, the introduction of two mandatory 15-minute coffee breaks in US factories was linked to marked increases in worker output. Caffeine’s effectiveness against drowsiness stems from its effect on the brain. It has the ability to block the binding of the neurotransmitter adenosine, which naturally builds up over the course of the day and causes tiredness. 

It’s widely believed that caffeine primarily alters sporting performance through its effect on the central nervous system (CNS). Its action on the CNS (and peripheral nervous system) can alter an athlete’s perceived effort, muscle pain, and the muscles’ ability to generate force

Even before these findings, concoctions containing caffeine were first used by athletes in the early 1900s, although its use hasn’t always been welcome in the world of sport… 

Legalisation of caffeine in sport

Between 1984 and 2004, caffeine was banned by the International Olympic Committee (IOC) and appeared on the World Anti-Doping Agency’s (WADA) list of prohibited substances due to its ergogenic effects. 

This was regulated by testing athletes’ urine post-competition. Caffeine concentrations greater than 12 ug/ml weren’t permitted (which equates to ~10 mg of caffeine per kg of bodyweight ingested orally over several hours; a dose that’s three times greater than the amount that reportedly enhances performance).

Caffeine was eventually removed from WADA’s banned list to help athletes avoid testing positive as a result of consuming ordinary substances like common-cold medication or drinking soda. 

In addition, it was agreed that caffeine consumption, for the most part, didn’t pose a health-risk for athletes.

Caffeine’s dark side

As far as psychoactive drugs go, caffeine is considered safe for consumption and is regarded as less addictive than other commonly used drugs like tobacco. 

But anyone who enjoys a cup of coffee knows that caffeine can have its downsides. There’s the dreaded caffeine ‘crash’ when the caffeine leaves our system and the adenosine, which has been building up throughout the day, all binds at once. 

There can also be side-effects from consuming too much caffeine or timing your intake poorly, including anxiety, headaches, nausea, jitters and insomnia.

What’s your caffeine tolerance?

Your experience of the potential side-effects will be influenced by your individual tolerance to caffeine, which varies widely from person to person. 

Some people are especially sensitive to caffeine’s effects, increasing the likelihood of adverse effects on sleep or feelings of anxiety, whilst others seem to tolerate a double espresso just before bedtime without any issues at all. 

Sensitivity and tolerance boils down to genetic variations in the enzyme which metabolises caffeine in your liver. As a result, people can be divided into ‘fast’, ‘slow’ and ‘very slow’ metabolisers, which appears to align with how sensitive a person is to caffeine ingestion

  • Fast metabolisers typically have a low sensitivity to caffeine and a higher tolerance, especially when taking it regularly. These are the folks who get the most benefits and least drawbacks from caffeine consumption
  • Slow or very slow metabolisers have a high sensitivity and low tolerance. As a result, caffeine stays in their systems for longer and just small amounts can have a high stimulatory effect 

It’s been observed that these genetic differences can influence the degree to which an athlete’s performance is affected by caffeine ingestion. 

A study conducted in 2018 found that cycling performance in a 10km time trial could be improved by 4-7% on average with a caffeine dosage of between 2 and 4 milligrams per kg of bodyweight, but only in individuals who possessed the genotype for fast metabolism. 

In contrast, cyclists with the genetic makeup for slow caffeine metabolism, performed nearly 14% slower when given a high dosage of caffeine versus a caffeine-free placebo. 

Can youth athletes use caffeine?

As most youth athletes should be taking part in sport largely for fun, it’s questionable whether encouraging the use of performance-enhancing ergogenic supplements is a good idea. But, I’ve taken a look at what the scientific literature says about the matter in case this is something you are considering for your own child, or yourself as a junior athlete.

The American Academy of Paediatrics recommends that those under the age of 12 shouldn’t consume caffeine at all, while those aged 12-18 should be limited to no more than 100-200 mg per day (or ~2.5 mg per kilogram of bodyweight). 

It’s important for children and adolescents to get a good night’s sleep for development and growth, so these recommendations have been put in place to avoid caffeine having a detrimental effect on sleep. 

Children and adolescents’ average body mass and size are obviously a lot smaller than adults, so caffeine can have much more of an impact on them. As a result, they can be more susceptible to its negative side effects.  

With that said, studies have suggested that youth athletes can safely use caffeine to benefit their performance, if it’s used sensibly. Just like adults, it’s important that individual sensitivity and tolerance is taken into consideration to avoid unpleasant side effects and sleep disturbances.

Children using caffeine should avoid doing so late in the afternoon or evening and it’s important to remember that caffeine will often be found in fizzy drinks and chocolate. 

Should you use caffeine in your fueling strategy? 

Your fueling strategy should focus first and foremost on replacing the three acute costs of taking part in endurance sport, namely carbohydrates, sodium and fluid

How you replace each of these will be very individual to you, but the science suggests that all athletes will benefit from an appropriate level of replenishment of each. 

Caffeine use can be seen as an optional, fourth performance-enhancing tactic as part of your fueling strategy, but it’s not appropriate for all athletes in the same way as carbs, sodium and fluid are. 

Whether you use caffeine or not will come down to your personal preference, previous experiences, sensitivity, tolerance, and habitual use of caffeine. 

Athletes who suspect that they’re especially sensitive to caffeine ingestion may negatively impact their performance by taking it, so avoiding consumption is actually the best way to aid their performance. 

Are you sensitive to caffeine? 

If your past experiences with caffeine suggests that you’re overly sensitive to its side-effects, then you may wish to consider avoiding caffeine and focus instead on other areas where you can make performance gains. For example, aim to prioritise quality diet and sleep and manage your pre-race stress levels. 

Are you a habitual caffeine user? 

On the other hand, if you’re a regular consumer of caffeine who hasn’t experienced adverse effects when taking it and you’re competing in an event where you feel caffeine may be beneficial (e.g. during an IRONMAN or ultramarathon), then you may wish to experiment with including some in your pre-training routine, or during very long training sessions

Have you used caffeine during training and races before?

If you’ve not taken caffeine before or during exercise previously, it’s strongly recommended that you test your intake during training first (remember the old adage: ‘Nothing new on race day’). 

Start with a low dosage (<3 milligrams per kilogram of bodyweight) and build up to a greater dosage over time if you handle it well and feel it’s beneficial to your performance. 

Be aware that during times of competition, you’ll naturally be more stimulated as a result of your adrenaline being higher in preparation for racing. As a result, managing your caffeine intake alongside your degree of nervousness is key if you’re to avoid overstimulation. 

A self-scoring system: how to work out if you should use caffeine

Image Credit: Precision Fuel & Hydration ©

How to use the self-scoring system:

1 point

If just 1 out of the 3 factors is true for you, then you may want to carefully consider whether introducing caffeine into your training or racing is the right thing for you. If you decide you want to use caffeine, build up your intake gradually.

For example, you might not have ever experienced any adverse effects when you’ve consumed caffeine before, but you’ve also never used it in a race scenario and you don’t take it on a daily basis.

2 points

If 2 out of the 3 factors apply to you then using caffeine could be a good idea.

For example, you consume caffeine every morning and you’ve never experienced any adverse effects, but you’ve never experimented with using it in races.

3 points

If all 3 factors are true then the risk of utilising caffeine in your racing or training is likely to be small. That said, be sensible and follow the recommended pre- and during exercise usage guidelines.

How much should you use?

Overall, there’s strong evidence that caffeine ingested before performance at a dose of 3-6 milligrams per kilogram of body weight (typically between 200 and 400mg of caffeine for adults) can benefit sports performance, as can taking some caffeine during longer events lasting more than ~4 hours. 

This is because the average half life of caffeine - i.e the time it takes for the concentration of a substance to halve in the body - is 4-5 hours (though some individuals metabolise it much quicker and slower than this). 

Learn more about how to use caffeine BEFORE exercise.

As caffeine is processed in the body, its stimulatory effects begin to wear off, therefore ‘topping up’ your caffeine levels throughout a race can be useful to stave off mental and physical fatigue (for example, you could use a PF 30 Caffeine Gel which contains 100mg of caffeine per serving). 

Learn how and when to use caffeine DURING exercise.

Further reading