Caffeine: what, when and how much to take

The performance benefits of caffeine


Many people consume caffeine regularly in everyday life. It can be found in coffee, tea, numerous soft drinks and chocolate, which provide anything from 30 to 150mg of caffeine. 

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In addition, after the ban on caffeine was removed from the WADA list in 2004, caffeine has become a widely used stimulant before and during exercise, and can be found in a range of sports products including gels, powders, drinks and tablets.

When used correctly caffeine can have a positive impact on a wide range of sports including endurance sports, high intensity activities, team sports and racquet sports.

How caffeine improves performance

There are various mechanisms by which caffeine can improve performance, including by stimulating fat oxidation, which means predominately using fat as a fuel source rather than using carbohydrate. 

This spares muscle glycogen (carbohydrate) for when it’s most needed, during the particularly tough parts of a triathlon. 

Caffeine also acts directly on the central nervous system, which results in increased mental alertness and reduced perception of effort, making the exercise seem easier.

How much to take

Consuming between 2-5 mg/kg body mass (140-350 mg for a 70 kg athlete) of caffeine can benefit performance, with more than 6mg per kilo of body mass showing no further benefit. 

In fact, 6 mg/kg can potentially be detrimental to performance because of increased heart rate and over arousal, which could impair concentration and consequently technique. 

In addition, consuming a high caffeine dose in the evening is not recommended as this could affect sleep quality, which over a long period of time can have a negative effect on performance.

When to take it

Caffeine typically takes up to 60 minutes to reach peak concentrations in the blood stream, which is key to ensuring the desired effects occur when they are most needed. 

Many athletes will use caffeine in their pre race strategy, consuming it 60 minutes prior to the start of a race. Alternatively or in addition, caffeine may be used towards the end of a race. 

For the latter strategy, consuming caffeine 60 minutes before the boost is needed would be ideal, for example in T2 during a half Ironman, to achieve a boost during the last part of the run.  

Using caffeine during recovery can help to promote glycogen resynthesis, which is particularly important for triathletes who train on consecutive days, and often multiple times a day.

Sources of caffeine

In terms of the best sources of caffeine, research found performance improvements to be similar when caffeine is consumed via coffee or capsule form. 

So, it comes down to practicality and which one is easier to transport and consume on the day.

Sports products such as gels, powders, drinks and tablets are typically more practical to carry with you and also provide additional benefits, such as a source of carbohydrate. 

The key takeaway here is that consuming 2-5 mg/kg body mass of caffeine either before or during a triathlon of any distance can benefit performance, assuming it’s consumed around 60 minutes before the effects are required. 

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Jill Leckey is the Senior Sports Nutritionist for Science in Sport (SiS).