Are you a “can’t-do-anything-until-i-have-had-a-coffee” kind of person? Or a “that-stuff-is-the-devil-and-leaves-me-awake-for-days” kind of person? Or somewhere in the middle?! 
— Dr. Sinead Roberts, in house nutritionist

Caffeine certainly has a weight of evidence to support its claim to enhance athletic performance. Indeed, it is one of few supplements we can claim with relative confidence as ‘proven’. Carbohydrates, protein, and creatine are others. But even so, this does not mean we should knock it back ad libitum … there are limits to its capacity, as well as potential downsides and doping (yes really!) factors to consider.

So … when might caffeine improve performance? 

When you are doing high intensity short, intermittent or endurance training. So, anything from a 100m sprint, repeated sprints, through to a cycling sportif! Also, when you need a fast reaction time, memory and vigilance, such as in a game of football. It is not yet clear whether caffeine enhances strength-power performance … some studies indicate yes, some no, and the reasons for the differences in findings are not clear. It is worth noting that most studies have been performed in males – the research in females looks promising, but more is needed.

How does it work?

Caffeine is a stimulant. We think it helps improve performance through many different mechanisms, some of which may be more dominant in some people and some types of sports than others. Some of the ways we think it acts …

  • Increasing the use of fat stores to supply energy, sparing our carbohydrate stores … running out of carbohydrates is a major factor in fatigue and carbohydrates are the only fuel for the highest intensity exercise, so if we can use them less at lower intensities (because we are using fats) we can potentially exercise harder and for longer! 

  • Improving neuromuscular function, so that our muscles contract faster and with greater strength

  • Increasing circulating endorphins, potentially meaning we feel less pain and fatigue when we train hard!

How much?

Typically results seem to be seen when 3-6mg/kg bodyweight is taken around 60 minutes before exercise. This allows time for the caffeine to reach the blood and exert its effects. Taking over 9mg/kg bodyweight in one go appears to show no further performance enhancement and increases the risk of nausea, vomiting, nervous jitters, insomnia and may risk taking you into doping territory … (more than 12ug/ml urine, under the International Olympic Committee standards)!! 

Whilst there can be significant levels of caffeine in coffee or tea, it appears that taking purified anhydrous caffeine is more effective at enhancing performance – this may be due to other components in the tea or coffee, and the extent to which the caffeine is absorbed. 

What about dehydration? 

Whilst caffeine is a diuretic, there is no evidence taking caffeine significantly increases the risk of dehydration during exercise. Proper hydration protocols should always be followed during exercise, to reduce the risk of dehydration from sweat losses. Interestingly, despite popular belief, it has been experimentally proven that coffee and tea are as hydrating as water!

Will I see the same effect if I am a regular caffeine drinker?

[or ‘insert other caffeine containing beverage’ drinker!]

The research suggests yes, however the effects may not be as prolonged.

Anything else to consider?

Yes! A few things …

There is so much variability in caffeine sensitivity between individuals, so test your limits before you start using caffeine before an important event. If you take too much for your level of sensitivity you could end up with stomach ache and the jitters … which is not going to help performance!! 

Caffeine appears to blunt the effect of creatine on muscle strength if they are taken together. As such, it is typically recommended that caffeine is avoided when you initially take creatine, and then to only take it pre-training. 

There is evidence that taking 3-6mg/kg bodyweight of caffeine with carbohydrates post exercise can increase the speed with which muscle glycogen (carbohydrate) stores are replenished, i.e. speed up recovery and refuelling. This could be important if you need to undertake another exhaustive carbohydrate dependent training session within 24 hours. However, intake must be balanced to ensure you don’t take in so much caffeine you induce insomnia … as sleep is also vital to recovery!!

Read more …

Goldstein et al. (2010). International Society of Sports Nutrition Position Stand: Caffeine and Performance.

Maughan et al. (2018). International Olympic Committee Consensus Statement: Dietary Supplements and the High-Performance Athlete.