Continued from Part I.
Knowing how caffeine works we can hypothesise about how it will effect our body and mind during sport. Combining this with what has already been formally tested and gather a good idea of how to use caffeine or whether to use it at all.
Physical effects:
Caffeine is usually absorbed at around 15 minutes after oral consumption and intuitively the adrenaline rush it produces seems to be ideal for surges of power. Sports like football, tennis and basketball constantly use a number of repetitive bursts that could benefit. Apart from being quickly absorbed, caffeine has a half-life of around 4-6 hours, all other things being equal. That kind of time is generally longer than your average football match and so it follows that caffeine could have potential benefit in endurance sports too.
A number of older articles (eg this one) have suggested that caffeine was unsuitable for short burst events, but since then reasearch has indicated significant advantages. Swimmers found that their VO2 max and velocity increased. In more universally applicable research, short sprinting bursts also displayed improved performance in both sprinters and the same group of reasearchers found similar advantages in a similar test with team athletes.
For endurance athletes the evidence is more consistent over a greater period of time, with significant increases witnessed as far back as the 70s. Apparently the first studies were on cyclists by David Costill who showed an approximate 20% decrease in fatigue, however I have been unable to source this article. There are several more recent studies which back this original research up. A Kalmar and Cafferelli study showed increased endurance in leg extensions of more than 16% in voluntary contractions. It has been shown that caffeine increases an endurance athelete's perception of fatigue and the placebo effect of caffeine has also been measured to significantly improve performance even in the absence of caffeine.
There are a number of other studies (I reccomend a quick search on PubMed) to a point where you could reach information overload. Generally the various studies' usefulness is limited due to the sample size or methodology flaws. This review of the existing caffeine literature sums it up rather nicely:
these benefits [of caffeine] are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear.
There is also the question of Caffeine's interaction with other supplements, in particular one of the most popular of modern supplements: creatine. Research by Vandenberghe et al has shown that caffeine has a very detrimental effect on creatine use for dynamic power, however both a Doherty et al study and a very recent Smith et al study showed that caffeine had no detrimental effect when combined with creatine. Smith's showed a creatine and caffeine (amongst other supplements) stack improved performance over a placebo. At first glance you might take the modern research over the later, but I would argue that the negative effects on creatine are still a significant concern.
Articles have raised concerns about Vandenberghes' methodology, focusing on a lack in wash-out periods for creatine. This is completely misplaced when you observe the placebo was in fact just creatine and so the methodology was sound. By contrast the stack tested by Smith et al does not isolate which ingredient is contributing to the performance so it could be any portion that is enhancing performance or even being held back by other ingredients. More damning is the fact the trial is single blind only and using a proprietary supplement. It is better to point to Doherty et al, who allows us to see that caffeine is useful in short sprint situations which leads us to an interesting situation. It appears as though caffeine negates the explosive power of creatine but not the mass and increases endurance in repeated interval exercise.
Cognitive effects:
If caffeine puts the body into an adrenaline fuelled state and constricts blood vessels in the brain, it could easily be expected that it would have negative effects on cognition. Some meta-analysis (an analysis of existing results from papers) paints a comprehensive picture of the effects. Perhaps surprisingly it appears that while there is no positive impact on memory recall, there is generally no negative effect either. Of specific interest to sports is that generally caffeine improves concentration, reaction time and passive learning, but not in intentional learning. Similarly its ability to improve mood is relative to dosage.
A negative side of caffeine's use as a supplement is using to the point of tolerance build up. As you would intuitively expect, individuals that regularly consume caffeine display less of the symptoms and withdrawal from heavy usage commonly results in side effects like headaches as blood vessels expand in the brain, tiredness and a lack of motivation. This is something athletes should certainly avoid. An increase in drowsiness is not beneficial physically or mentally, nor is a dependence on caffeine to operate at a previous baseline level of performance.
In Part III we will analyse the usefulness of caffeine as a sports supplement.
Sources and further reading:
http://www.ausport.gov.au/ais/nutrition/supplements/supplement_fact_sheets/group_a_supplements/caffeine
http://www.trifuel.com/triathlon/nutrition/caffeine-and-endurance-000402.php
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