How long does caffeine stay in the body, and for how long do you feel its affects?

Caffeine is possibly the most effective legal drug in triathlon, says James Witts. Here he explains how much time it spends in the body and for how long you can feel its affects

How long does caffeine stay in the body for?

 Caffeine is possibly the most effective legal drug in triathlon. Its benefits include reducing perception of effort, burning more fat for energy, improving decision making and increasing muscle power. So proven are its performance-enhancing effects that it was once banned by WADA (World Anti-Doping Agency). 


To boost your performance, you’re looking at anywhere between 3-4mg of caffeine per kilogram body mass. As an example, that means between 210-280mg of caffeine for a 70kg triathlete. Starbuck’s own-brewed coffee comes in at 20.6mg of caffeine per fluid ounce so over 240mg for a 12fl oz cup.


When should you take caffeine during a triathlon?

These performance effects are at their highest when caffeine levels peak in the blood, which can vary between 15 and 45mins after consumption. Caffeine has a half-life of up to five hours, meaning if you consumed 100mg of caffeine, you’d still have 50mg of caffeine in your body after five hours. In both peaking and half-life, however, it’s hard to be totally prescriptive as factors that impact on how quickly it’s metabolised by the liver include age, bodyweight and how sensitive a person is to caffeine.

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