This blog explains how a triathlete, cyclist or runner might best make use of caffeine to improve their performance, based on the most recent research. Caffeine is one of the most common supplements used in endurance sports, and one of only five to be considered to have a strong evidence base by the International Olympic Committee (IOC) in their recently published Consensus Statement on Dietary Supplements. 1

How would caffeine improve my endurance sports performance?

Caffeine interacts with the adenosine receptors, which are widely present in your brain, skeletal muscle and fat stores. It is now thought that the primary effect of caffeine is to reduce your perception of fatigue by its effect on the brain.2 Interaction with the adenosine receptors stimulates your central nervous system, improving neuromuscular function and helping to maintain a higher concentration of the neurotransmitter dopamine. This results in increased alertness and focus, decreased perceptions of pain and lower ratings of perceived exertion. All these factors help you to sustain your motivation to race. Adenosine receptors are also involved in the workings of your body clock, with an increase seen throughout the day and a decrease at night. Caffeine binds to the receptors, blocking the adenosine, and this causes you to remain alert for longer. It can also help you to feel awake more quickly for early morning race starts.

How much caffeine do I need to take?

Until 2004, caffeine was on the World Anti-Doping Agency’s (WADA) banned list for urine concentrations of greater than 12mg/l. This was changed because of new research indicating that caffeine had a performance enhancing effect at lower levels than previously thought, levels that could be contained with the habitual consumption of common drinks and foods such as coffee, tea and chocolate.

The current recommendation for endurance sports is to take around 3mg (max 6g) of caffeine per kg of body weight around an hour before your event start, and then to top up with 1-3 mg/kg per hour during your event alongside a source of carbohydrate. 1 For example, a 2016 study on trained cyclists showed a benefit in a subsequent time trial when either 1.5mg/kg or 2.9 mg/kg of caffeine was taken after two hours of moderate pace cycling, compared with taking a placebo, but the higher dose produced a faster TT time. 3

In long distance events, eg Ironman or all day cycling sportives, it might be advisable to top up with caffeine only in the latter part of the event as fatigue starts to set in, to prevent caffeine overload which might result in gut issues. Using this strategy, a 60kg athlete might drink coffee containing 180mg of caffeine prior to the start of a 12 hour event (3 shots of espresso or two mugs of filter coffee), then start using gels containing 30mg of caffeine in the last 3-4 hours. In shorter endurance events, you might choose to use caffeine throughout at 1mg/kg of body weight per hour.

How should I get my caffeine?Cup of coffee - endurance sports nutritionist

Research suggests that both drinking coffee containing caffeine and taking caffeine in the form of tablets, chewing gum or contained in gels, chews or sports drinks will have a similar effect on performance. A 2013 study 4 showed that trained cyclists achieved similar performance times and power outputs in a time trial after drinking either instant coffee with 5mg/kg of caffeine or fluid containing the same amount of a caffeine supplement. Results from both were significantly better than when decaffeinated coffee or a placebo was taken prior to the time trial.

Taking caffeine as a chewing gum allows for quicker absorption compared with other forms of delivery such as

drinking coffee or taking caffeine tablets, although it does not increase the total amount of caffeine absorbed over time. Peak caffeine concentrations appear to be reached around 5-15 minutes after chewing gum, compared with 30-45 minutes after taking caffeine pills. 5 If using chewing gum, it is important not to take it too soon. It is likely that products such as caffeinated chewing gum or newly available mouth washes and nasal sprays are best used in sports with intermittent intensity, such as football, or prior to short high intensity efforts, eg sprinting. For an endurance athlete, drinking coffee prior to the start of an event and using sports nutrition products such as bars, gels

and chews which contain caffeine as well as carbohydrate during the race is likely to be a more effective strategy, avoiding the need to take on caffeine in a separate form such as tablets or gum. You can also use caffeinated drinks like Coke (9mg per 100ml) or Red Bull (34mg per 100ml) if these are available on the course. Notice the difference in caffeine content between these two popular drinks!

The amount of caffeine in coffee does vary – for example, Starbucks coffee contains higher than average amounts of caffeine – and it is also found in smaller amounts in tea. There is roughly 95mg of caffeine in a 250ml mug of filter coffee (180mg at Starbucks) and 63mg of caffeine in a single shot of espresso (75mg at Starbucks). Instant coffee generally contains less caffeine than filter or espresso, as little as 30mg per 250ml mug. There is around 25mg of caffeine in a 250ml mug of tea. So, it is important to check how much caffeine you are consuming in your pre-race coffee, particularly if you know you are sensitive to its effects. All sports nutrition products containing caffeine will give the amount on the label, so make sure you check this when planning your race nutrition strategy, as there is huge variation between brands and even between different products in the same brand.

Should I use caffeine in training?

You should always practice your nutrition plan before race day, to ensure that your chosen products work well for you and do not result in any adverse effects, eg digestive upsets. Using sports nutrition products containing caffeine, such as gels, drinks, bars or chews, should be part of this process, particularly on your longer training sessions, and it would be worth experimenting with different amounts of caffeine to assess the impact it has on your performance. One idea might be to do repeated time trials over a period of three weeks, the first using no caffeine, the second with a low dose of caffeine (eg 1.5 mg/kg) and the third with a higher amount (eg 3 mg/kg). Make sure that everything else stays consistent, eg pre-TT nutrition and coffee intake, and of course your route or time on the tre

admill or indoor bike. It would also be advisable to trial your planned pre-race coffee intake along with your pre-race breakfast. However, there is no need to use caffeinated products before or during every training session.

There is evidence that caffeine can be used to support low-glycogen training, when you deliberately train in a fasted or low carbohydrate state to increase the number of energy-producing mitochondria in your muscle cells, an adaptation to training which enables you to improve endurance performance. One study showed that ingesting 3mg/ kg of caffeine was shown to increase power input during high intensity interval training by 3.5% compared with placebo when cyclists were glycogen-depleted and by 2.8% when they had normal glycogen

availability. 6 Another study showed that the reduced performance seen when completing a 4km cycling TT in a glycogen depleted state, versus normal levels of glycogen, was restored when the cyclists were given 5mg/kg of caffeine one hour beforehand, albeit with a higher contribution from the anaerobic energy system. Performance was not restored when a placebo was given instead of caffeine. 7

Should I stop drinking coffee in the days before an event?

when to have caffeine to assist in an endurance eventThe evidence now suggests that there will be no benefit in reducing or stopping your coffee intake if you want to use caffeine to help improve your performance. It used to be thought that people habituated to drinking coffee did not respond as well to using caffeine to enhance performance as people who usually avoided sources of caffeine. So, the general advice was to stop drinking coffee in the days or even weeks before an event. However, several studies have now shown similar performance in heavy coffee drinkers when consuming caffeine without a withdrawal period as seen when they had a four day withdrawal period. A 2017 study also tested 6mg/kg of caffeine before a 30 minute time trial on endurance cyclists who were either low (1 cup per day) moderate (3 cups per day) and high (5 cups per day) coffee consumers. The benefits of the caffeine were not significantly different between the groups, and all saw an improvement compared with when taking a placebo (2.4%) and not taking a supplement at all (3.3%). 8

Does caffeine work for everyone?

The short answer is probably not, but we don’t have enough information yet to fully explain why. Research in the relatively new field of nutrigenomics – the interaction of nutrients and genes – suggests that genetic differences account at least partially for why some people do better on caffeine than others. One of the genes involved in the detoxification of caffeine in the liver is called CYP1A2. Everyone carries a variant of this gene. Those who carry the AA variant appear to be “fast metabolisers” of caffeine, ie they process caffeine quickly. Those who carry the CC variant appear to be “slow metabolisers”, ie caffeine takes longer to have an effect and longer to leave their body. Everyone else carries the AC variant, which has a less obvious effect.

A study carried out in 2018 showed that consuming both 2mg/kg and 4mg/kg of caffeine improved performance in a 10km cycling time trial, but only in those cyclists carrying the AA variant – the fast metabolisers. Those carrying the AC variant saw no effect and those with the CC variant – the slow metabolisers – saw a reduction in their TT time when they consumed the larger amount of caffeine. The researchers suggest that an individual’s CYP1A2 genotype should be tested and considered when deciding whether to use caffeine to support endurance performance. 9

Although there is plenty of evidence for caffeine having a positive effect on performance, this comes from studies reporting their results as an average. However, the individual results from the athletes in a study taking caffeine at the same dose and in the same conditions often varies widely. It is likely that this is at least partly explained by genetic differences. More research is required to understand this and to develop more specific guidance on using caffeine. 10

In the meantime, you will probably already know how sensitive you are to caffeine. You might find it keeps you awake if you drink it after a certain time of day, suggesting you are probably a slow metaboliser. Or that it makes you anxious or nervous, in which case that pre-race triple espresso may not be a such a good idea.  Or that you need the toilet soon after a cup of coffee, which might cause problems if you take on too much caffeine during a race. Use this information to help you to develop a caffeine plan that is right for you – and don’t forget to practise it in training.


  • Consume around 3mg/kg of caffeine from coffee 1-2 hours prior to your event.
  • Take on a further 1-3 mg/kg per hour during your event from gels, bars, chews, sports drinks, or Coke/Red Bull if available. In all-day events, use caffeine only in the latter stages.
  • There’s no need to stop drinking coffee or using other forms of caffeine in the days/weeks before your event.
  • Caffeine doesn’t work for everyone. Trial it in training. If you experience side effects from caffeine that adversely affect your race, stop using it.

Jo Scott-Dalgleish BSc (Hons) is a BANT Registered Nutritionist, writing and giving talks about nutrition for endurance sport. Based in London, she also works as a Registered Nutritional Therapist, conducting one–to–one consultations with triathletes, distance runners and cyclists to help them eat well, be healthy and perform better through the creation of an individual nutritional plan. To learn more about these consultations, please visit


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