martes, 11 de octubre de 2016

Caffeine & Endurance Exercise

1,3,7-trimethylxanthine, although you may not have heard it called that before, I can almost guarantee that it is your favourite stimulant. For most of us not a day goes by without a dose of caffeine, usually in the form of tea, coffee, chocolate, coca cola and the seemingly ever increasing number of energy drinks. Ever since caffeine was taken off WADA’s banned list in 2004 you have been able to find more and more sports nutrition products that contain caffeine, in fact, it’s actually quite difficult to find gels and tablets that don’t contain caffeine.

The efficacy of caffeine for the use in sport, especially endurance sport is well established and widely used by athletes, so much so that WADA have placed caffeine on to their “watch list” for 2016. Which means they are concerned that it may be being overused or abused during competition and so they want to keep an eye on it. The Australian Institute of Sport place caffeine in category A of their supplement list1 which means that there is sound evidence for a performance improvement. This post will not be concerned with whether caffeine works or not because we know it does. With this post I hope to clear up some of the other questions that surround the use of caffeine as a sports supplement.

How much to take and when to take it

As with many supplements there is always a trend towards the thinking of “more is better”however in reality there is always a point where more no longer becomes better and soon becomes unpleasant. The earlier caffeine studies showed that a dose of around 6mg/kg of body weight had a positive effect on an 1hrs cycling performance. That is the equivalent of around 300-500mg of caffeine (a lot!), however, it soon became apparent that equally positive results were found with smaller doses of caffeine, ~200mg. And so it was concluded that caffeine does in fact improve performance but it appears only to be dose dependant up to a point, and then further ingestion of caffeine does not result in further improvements2,3.
Recently on his website4 Asker Jeukendrup reviewed a paper that looked at caffeine and longer duration cycling. Subjects rode for 2 and a half hours and then performed a time trial. Subjects either ingested 100mg caffeine, 200mg caffeine or a placebo 40 minutes before the time trial. Subjects who ingested the 200mg performed the TT quickest followed by 100mg.  
So the take home message is that if you have an event/training session that will last around an hour then around 200mg of caffeine an hour before your event will do the trick. Or if you are going on a longer ride and want a pick me up for the final climb or last hour of riding then take your 200mg caffeine either 40mins – hour before that climb or last bit of riding.

Source of caffeine

I’ve said this before but a classic error of dietitians and exercise coaches is to talk in terms of weights and nutrients but not in a way that most people understand. What does 200mg of caffeine look like? One coffee? Ten? Below is a table 2,3,5 with the caffeine content of several drinks and sports nutrition products to give you an idea of what 200mg would look like.

Serving size
Amount of caffeine mg
Coffee percolated (Italian coffee maker)
150mls (about halfway up of a normal coffee mug without milk)
Coffee espresso
1 espresso
Coffee instant
150mls (black)
10 -50 depending on length of time you leave the bag in the cup
Chocolate bar
Coca Cola
Can (330mls)
Red Bull
Can (250mls)
Can (553mls)
176 (plus a bucket load of sugar)
Science in Sport GO Hydro+caffeine tablets
One tablet (4.5g)
Science in Sport GO Caffiene Gels
One gel 60mls
Overstims Cafein’Gel
One gel (29g)

There is also the question of whether coffee is as effective as a specific caffeine containing sport product. Sports nutrition companies would obviously argue that it is not and would encourage you to use their products instead. However, coffee has been shown to be as effective7 as a caffeine containing sports drink in a cycling time trial. Obviously coffee during a ride or run is not particularly practical, unless you don’t mind stopping at a café. So I would recommend gels or drinks during the event but if you want and early caffeine boost during your training session than it appears a strong coffee will not only be a lot nicer than a gel or sports drink but will also be as effective.

How does it work

In the early studies involving caffeine the benefits were thought to be because caffeine increased fat utilisation during exercise and thus reduced glycogen utilisation enhancing endurance performance2. However due to more recent evidence the current explanation is that caffeine reduces perception of fatigue and allows people to maintain a higher intensity for a longer period of time6

Caffeine and recovery 

When thinking about caffeine and recovery an obvious issue is sleep. Sleep is essential to performance and poor sleep can lead to several problems, most importantly for sports people are, reduced training capacity and impaired immune function. This may sound like an obvious point but as most of us amateur athletes have to fit our training around our lives, (jobs, family etc.) a lot of us train in the evening. As caffeine can take from 3 – 6 hours to clear the blood streamit is not recommended that you use caffeine for a training session in the evening.
Interestingly there is some data that suggests that post exercise caffeine ingestion may reduce perceived leg pain after a long cycling event9. I would say we need more research before we can confidently recommend caffeine after exercise, however, if you are anything like me then a cup of tea or coffee is part of the post ride ritual anyway. 

Does it dehydrate you

The belief that coffee dehydrates you is as old as the hills but is there really any truth in it? As pointed out by the Journal of the International Society of Sports Nutrition in their position stand on caffeine8 it is important to separate caffeine consumption at rest (in the office for example) and caffeine consumption during exercise. While there may be some evidence that caffeine can increase urinary output at rest, this is not the case for during exercise8.
The bottom line is if you maintain appropriate hydration levels both at rest and during exercise then caffeine consumption will not lead to you being dehydrated.   

So in conclusion
  • Around 200mg of caffeine taken 45-60mins before the effects are needed
  • Can be in the form of coffee/drinks/gel/tablet
  • Does not hinder recovery but caution is needed when taking before planning to sleep
  • Does not dehydrate you 
For more information on caffeine, supplements or our sports nutrition packages please contact us on or via Twitter @DieteticodRB and Facebook @GabinetedeRuedaBradley

  2.  Burke, L, 2007. Practical Sports Nutrition, Human Kinetics
  3.  Jeukendrup, A; Gleeson, M; 2004. Sport Nutrition, Human Kinetics
  5. , ,
  6.  American College of Sports Medicine, 2016, Nutrition and Athletic Performance, available at
  7.  Hodgson, A, B et al. 2013, The metabolic and performance effects of caffeine compared to coffee during endurance exercise, PlosONE , 8, 4
  8.  Goldstein et al. 2010, International society of sports nutrition position stand: Caffeine and performance, Journal of the International Society of Sports Nutrition, 7, 5  
  9.  Caldwell, A; et al. (2015) "EFFECT OF CAFFEINE ON RECOVERY FROM AN ENDURANCE CYCLING EVENT," International Journal of Exercise Science: Conference Proceedings: Vol. 11: Iss. 3, Article 39. 

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