Nutrition feature: Emma Barraclough, sports nutritionist at SiS (www.scienceinsport.com), looks at the effect caffeine has on performance
Caffeine products have increased in popularity in recent years; there are a number of reasons behind this, a key one being that people consume caffeine more widely now in various formats. Besides the traditional soft drinks, you can now buy caffeine tablets, energy drinks, energy shots and even chewing gum, and people’s general tolerance for caffeine has increased with many coffee shops now serving double shots of espresso as standard, and higher doses being present in many modern soft drinks.
The scientific understanding of the effect caffeine has on performance has also increased; caffeine now has one of the strongest evidence bases amongst all nutritional supplements for sport, including endurance exercise, which has widened the use further.
Caffeine acts centrally on the brain to lower the perception of effort, which is particularly noticeable in longer events such as ultra running. In ultra distance events mental tiredness - as well as physical fatigue - plays a large role in determining performance as the event progresses, and caffeine can help to maintain performance in this situation.
Spriet et al (2014) published a review on caffeine and concluded that 3-9mg of caffeine per kilo of body mass can positively impact performance, with levels of around 5mg per kilo of body mass recommended for endurance sports such as distance running. Cox et al (2002) found that time trial performance improved by 3% with 6mg per kilo of body mass, which could equate to as much as 7 minutes off a four hour marathon.
As an example, the new SiS GO + Caffeine Double Espresso gel (HERE) provides 150mg of caffeine with 22g of fast release carbohydrates; two of these would be the equivalent of a 5mg per kilo body mass dose for a 50kg runner.
To benefit from caffeine in your running performance, bear in mind that it can take 30-60 minutes after consumption for the level to peak in the blood, so if you’re doing a short duration event (less than 60 minutes) you should take it before you start.
If you’re doing a much longer event, e.g. marathon distance or further, you should save your caffeine intake for the last two hours when your fatigue level is likely to catch up with you, which can be particularly effective if you’re doing an ultra run through the night when sleep deprivation is a factor.
When using any caffeine product, potential side effects should always be considered. At rest caffeine has been questioned as a diuretic, however during exercise this does not seem to be the case. Zhang et al (2014) published a meta-analysis with a median caffeine dose of 300mg and found that exercise negated the increased urine volume that occurs when the same caffeine dose was given at rest.
Everybody’s sensitivity to caffeine is different, so it should always be tried in training and in small doses initially. In order to promote good sleep, caffeine should be avoided for at least 2-3 hours before bed.
References:
Cox G. R., B. Desbrow, P.G. Montgomery, M.E. Anderson, C.R. Bruce, T. A. Macrides, D. T. Martin, A. Moquin, A. Roberts, J.A. Hawley, and L. M. Burke. (2002) Effect of different protocols of caffeine intake on metabolism and endurance performance. Journal of Applied Physiology 93: 990-999
Spriet L. L. (2014) Exercise and sport performance with low doses of caffeine. Sports Medicine (44) Suppl 2:175-84.
Zhang Y., Coca A., Casa D.J., Antonio J., Green J.M. and Bishop P.A. (2014) Caffeine and diuresis during rest and exercise: A meta-analysis. Journal of Science and Medicine in Sport (9) S1440-2440
Emma Barraclough is a Sports Nutritionist at SiS (www.scienceinsport.com). She has worked with Great Britain Ice Hockey since 2006 and provided nutritional consultancy support to athletes in a range of sports including running, triathlon and rugby. She regularly represents Great Britain as an age group triathlete and has completed six Ironmans.
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