Nutrition clinic: Caffeine explained

Does caffeine boost your running? It's a debated issue in the sports world, Dr James Morton explains how to use it correctly to aid your running.


by Dr James Morton

Welcome to our nutrition blog by Dr James Morton (Senior Sports Nutritionist for Science in Sport (SiS) and Senior Lecturer in Exercise Metabolism & Nutrition at Liverpool John Moores University), where he will be giving advice on nutrition, dispelling fuelling myths and offering his tips every month. If you have a sports nutrition question or area you'd like to see covered in the blog, email editor@runnersworld.co.uk with the title SiS Blog.


Lots of foods and drinks in our everyday lives contain caffeine. It’s a drug that can be used to help you perform better in training and racing, if used correctly.

Caffeine is without doubt one of the world’s most popular and commonly consumed drugs. When we think of caffeine, most of us immediately consider it synonymous with coffee and tea though in reality, caffeine is contained in many other foodstuffs such as soft drinks and chocolate etc. As such, many of us already consume caffeine on a daily basis due to our everyday eating patterns.

Of all of the sports nutrition products available on the market, caffeine is probably the one that has the strongest and most consistent scientific support. Caffeine has been shown to improve both mental and physical performance across a range of sports such as running, cycling, rowing, swimming and even team and racquet sports. Caffeine is thought to improve performance through multiple mechanisms that consist of acting directly on the central nervous system, altering substrate metabolism to promote fat oxidation and also acting on muscle fibres themselves so as to increase strength and power. When taken together, this means that caffeine can help reduce the perception of effort (i.e. make the exercise seem easier), spare muscle glycogen utilization (leaving more glycogen available for hard parts of the race) and ultimately, help us run quicker.

Caffeine is rapidly absorbed and peak caffeine levels in the blood typically occur approximately 45-60 minutes after ingestion. As such, most elite athletes consume caffeine as part of their pre-race strategy. However, it is worth noting that caffeine may also be used practically during the race itself in order to provide a boost towards the later stages of the race. For runners, in particular, this would mean strategically consuming caffeine approximately 45 minutes prior to the part of the race in which the athlete may need a physical and mental boost.

For caffeine to be effective, the consensus from all of the research is that beneficial performance effects can be achieved with as little as 2-5 mg per kg of your body weight. For a 75 kg athlete, this would equate to 150-375 mg of caffeine and it should also be consumed in the 30-60 min period prior to exercise. There is no clear dose-response relationship, however, and in fact deteriorations in performance have been observed with doses exceeding 6 mg per kilogram body mass. In such situations, these large doses often induce negative symptoms such as increased heart rate, irritability and shortness of breath etc. In effect, too much caffeine can be bad for you and some individuals are more susceptible to others. Furthermore, consuming high doses of caffeine prior to or during night races and competition can also be problematic given that its effects can last for many hours and hence, sleep quality can be negatively affected.

Previous studies have traditionally shown that consumption of caffeine in the form of capsules, gels and energy drinks are superior to the common approach of consuming coffee, likely due to other compounds within coffee that may offset the performance boosting products of caffeine. However, more recent research from the University of Birmingham (led by Dr Adrian Hodgson and Prof Asker Jeukendrup) has shown that 5 mg/kg of caffeine when consumed in either coffee or capsule form induces similar performance improvements compared with both decaffeinated coffee and placebo capsules. As such, a strong coffee may be a suitable approach for a pre-race strategy where as caffeine rich gels and drinks would be more practical during the race itself.

In addition to race day performance, caffeine may also be a useful aid to use during a periodised training schedule. For example, Prof John Hawley has shown that adding caffeine to post-exercise carbohydrate feeding enhances muscle glycogen re-synthesis. As such, our group in Liverpool John Moores University subsequently demonstrated that consuming caffeine after a morning training session actually enhances training capacity during an afternoon training session. Furthermore, caffeine can also be used as a pre-training aid for those training sessions that are deliberately commenced in a glycogen depleted or fasted state (in an attempt to enhance training adaptations) as caffeine has been shown to partially rescue the decrements in training intensity that occurs when training is performed in low carbohydrate states.

The take home message is that caffeine, when taken at the optimal time and in the correct form and dose, can be a highly effective approach to help you train harder and run quicker.

To find out more about the SiS GO range of caffeine products, please visit: http://www.scienceinsport.com. The new Cola-flavoured SiS GO + Caffeine gel contains 75mg of caffeine.


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