Thursday, 25 August 2011

Caffeine and Athletic Performance

Remember last post, when I promised I would go over protein and athletic performance?  I lied.  Well I didn't think I did, but protein will have to wait because I just came across a very interesting study from 2010 published in the Annals of Nutrition and Metabolism.  If you don't feel like reading my entire article, I'll give you the 11 word summary: drink some coffee before a race, and you might go faster.

Is Caffeine Actually Allowed?

First, before we get into the the details of why and how to use caffeine, we have to establish if its use constitutes cheating.  Well, prior to 2004, if you had a certain amount in your urine, then you would have been accused of using a performance enhancing substance.  However, since then, it has been entirely taken off the World Anti-Doping agency's list of prohibited substances:

"The following substances included in the 2011 Monitoring Program (bupropion, caffeine, phenylephrine, phenylpropanolamine, pipradol, synephrine) are not considered as Prohibited Substances." -2011 Prohibited List, International Standard, World Anti-Doping Agency

So, if you decide to drink an extra cup of coffee to see what happens, you will not be breaking any rules by doing so.

Does it Actually Work?

For endurance activities, the short answer is yes.  A large number of studies referenced in the review below have shown that caffeine can improve performance in sport specific endurance events including running, cycling and cross-country skiing. 

By contrast, for high power/strength related tasks (such as sprints), there is no evidence showing that caffeine will help.  However, there is no evidence showing that it has a negative impact on performance either.  Essentially, (to coin scientists' favourite statement), more research is needed.

How Much?

So, you're an endurance athlete, and you're trying to decide how much to take.  This is the basic rule of thumb:
  • 2–6 mg per kg of body weight 1 hour before exercise
          • OR
  • 0.75–2.0 mg  per kg of body weight during exercise
These numbers come from the caffeine levels a majority of the studies used when showing caffeine had a positive impact on performance.  However, as you can see, there is quite a range, and thus it is very important to play around within these ranges to see what works best for you.  If you are a habitual coffee drinker, you will likely be at the upper end of the spectrum (6mg/kg) while if you rarely consume caffeine, you will be close to the 2mg/kg.

How Much is 1 mg??

Yeah, 1mg of caffeine does not mean anything to me either.  Here are some common dietary sources, and the amount of caffeine they contain:
  • Coffee 250 ml
    • Brewed100–150mg
    • Drip125–175mg
    • Instant 50–70mgTea
  • Tea 250ml 
    • Green (medium) 25–40mg
    • Black (medium) 40–60mg

  • Cola drinks 355 ml 35–50mg
  • Chocolate 50mg
    • Dark 20–40mg
    • Milk 8–16mg
So, how do you apply these numbers?  Well, for me, I am about 70kg.  If I were to attempt to use caffeine within the middle range of recommended doses, I would want to consume about  3mg of caffeine per kg of body weight.  Thus, I would want to consume 70kg(3mg/kg)= 210 mg total.

Thus, 1 hour before competition, somebody my size could attempt ingesting 210mg of caffeine, and could do so by drinking about 500ml of brewed coffee.  Not bad, many of us drink that much coffee to begin with anyway!

How Does it Work?

Disclaimer: This is the scientific section, I will not be offended if you skip it (this time). 

The classic studies on the beneficial effects of caffeine pointed toward the positive effects being related to caffeine's role as an adenosine receptor antagonist.  Adenosine receptors are found in a number of cell types throughout the body.  Speaking very generally, once they are activated, they have an inhibitory effect on the cell in question.  So, if we are talking about a heart cell, then the rate of contraction of that cell will decrease.  If we are talking about a cell containing fat, then it will cause that cell to retain and store more fat.

As a adensoine receptor antagonist, caffeine essentially will stop the adenosine receptor  from triggering the effect it is supposed to trigger.  In other words, it will stop that inhibitory influence from happening.  So, if we are talking about the fat cells again, caffeine will cause fat release into the blood stream and also discourage fat storage.  It was, therefore, thought that this would provide more fat readily available to be used to energy during exercise, sparing our carbohydrate stores.

However, more recent studies have shown that this may not be the case.  While it is true that caffeine will increase fat mobilization and decrease fat storage, these newer studies also show that this has no impact on saving our carbohydrates.  So, something else must be going on to account for the increased performance.

Looking beyond caffeine's influence on our fuel sources, one very prominent theory as to why caffeine works to improve performance is its direct impact on our nervous system.  A number of studies have shown not only that caffeine ingestion will result in a decreased perception of exertion during an endurance activity, but that it can also decrease how much pain an athlete experiences.  In other words, your central nervous system is wired, and you are less susceptible to mental fatigue.

My Thoughts

First of all, it is clear that caffeine at the ranges listed above likely does have a positive impact on performance in endurance events.  However, as you probably noticed, I did not mention how much of an impact it will have.  The reason for this is simple:  we do not really know.  The evidence is all over the place, some showing caffeine will have a drastic impact, lots showing it will have a minimal positive impact, while some showing that it will have an equivocal effect on performance.

If you are curious about how caffeine can help you, the best thing you can do it play around with different levels within the given ranges during training.  Experiment with what works best for you and your specific event, and stick to it.  Also, always pay close attention to side effects (such as rapid heart beat, tremors, upset stomach).

Before you decide to use caffeine, I also recommend thinking about why you are using it.  If caffeine works by stimulating your central nervous system, do you really need it, and do you really want to rely on it?  There are definitely other ways to get yourself pumped up and excited before and during a race (such as music, people cheering for you, and creating internal goals/sources of motivation).  But, either way, it might be a cool thing to experiment with! 


World Anti Doping Agency, 2011 Prohibited List, International Standard:

Ann Nutr Metab 2010;57(suppl 2):1–8

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