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

Tuesday, 9 August 2011

Nutrition and Athletic Performance: Part 1

What about Pizza?
Recently, I have had quite a few people ask me about various components of nutrition and its role in athletic performance.  The good news is that there is a huge amount of research on this topic, and the basic principals are very well understood.

Proper nutrition is extremely important in any sport, but undoubtedly becomes more important the longer the event lasts.  When I think back, it is almost comical when I count the number of races and training sessions that I have struggled through due to poor nutrition.  For instance, once during my cross-country days in university, I was busy with school and thus made the incredibly intelligent decision to skip eating to save time.  Then, when 3:30pm rolled around, I suddenly realized that,  "hey, I will need some calories to get me through the 4:00pm workout."  Well, my then 18 year old brain analyzed the situation, and came up with a seemingly flawless solution: 2 slices of greasy pizza (with copious amounts of dipping sauce, of course), and a coke.  Needless to say I bonked hard, barely finished the workout, and was left baffled.  Why did this nutrition strategy not work nearly as well as anticipated? 

Fortunately, since then I have learned exactly what it takes to optimize performance, especially in endurance sports.  Since it is a complicated issue, today I will talk about only one important component: carbohydrates.

How Much Should I Eat?
For endurance activities, carbohydrates are vital as they function as your primary source of fuel.  The amount of carbohydrates you consume during a regular training regimen is obviously quite variable depending on the training volume.  A general rule of thumb though is that you should ingest 6-10 grams of carbs per kg of body weight per day.    So, for me, I am about 71kg, so I need to ingest up to 710grams of carbohydrates per day.  That is about 32 pudding cups- delicious!

To get a more specific idea of how much and when you should be eating, first let's go through where your energy is coming from.   

When You Use What
Disclaimer: If you're bored by science, skip this section! 
It is important to understand that depending on how long your sport lasts, you utilize different sources of energy from within your body.  Here is a breakdown of when each fuel source kicks in: 
  1. Activities lasting 1-3 seconds (i.e. golf swing): Your body uses ATP already present.  ATP is essentially energy waiting to happen, ready to be used virtually instantly.
  2. Activities lasting 4-7 seconds (i.e. short sprint): You body again uses ATP along with the help of creatine phosphate (which basically helps to replenish depleted ATP levels)
  3. Activities lasting 10-30 seconds (i.e. hockey shift): Again ATP and creatine phosphate is used, but this time fast glycolysis is also used.  Fast glycolysis is the process of breaking sugar down that is readily available in your blood.
  4. Activities lasting 1-3 Minutes (800m run): Now your body not only utilizes sugar already in the blood, but it also taps into your glycogen stores.  Glycogen is essentially chains of sugar stored in your muscles and liver, waiting to be mobilized and used for energy.
  5. Activities lasting 3 minutes or more: You still are using sugar and glycogen, but you also start to tap into fat stores.  I will talk about this more in a future blog.

How To Eat Carbs Days Before
From above, it is clear that for any activity lasting more than 10 seconds, carbohydrates are extremely important.  In addition, any activity lasting over a minute, glycogen becomes a valuable source of energy.  For longer events (i.e. vigorous activity lasting 40-150 mins), about 70% of your energy comes from glycogen.  Thus, it only makes sense to pack as much glycogen into your muscles as possible prior to a competition.  This is the best way to do it:
  1.  During regular training, consume carbohydrates at a proportion of 60-70% of your daily caloric intake (this may go up to 80% if you train very long hours, i.e. for cycling).
  2. 4 days prior to competition, exercise to exhaustion while consuming a low carb diet (i.e. force yourself to completely deplete your carb stores).  This will not be fun!
  3. In the next 3 days, train easily, and consume a carbohydrate rich diet (up to 80% of your total diet).
  4. Do not train the day before competition.
This method has been shown to induce a phenomenon called super-compensation.  By implementing this method of carb loading, research has shown that the muscles are effectively able to hold 200% of the glycogen they normally contain.  Thus you have more glycogen, more energy, and as a result a longer lasting level of high performance.

How to Eat Carbs on Race Day
So after you have completed the perfect carbohydrate load by following the sequence above, now the question becomes; how do I eat the morning of a competition?  While there are many different things to consider, the one universal rule that should be followed is: eat your last large meal at least 3 hours prior to competition.  So, if your race is at 8am, make sure you are done breakfast by 5am.  Here's why:
  1. When you eat, the hormone insulin is released into your blood.
  2. Insulin's job is to signal the body to store the food that was just ingested (either in fat or glycogen).
  3. This is BAD for performance, because we need to access those energy sources as quickly as possible, but insulin is working against us, trying to store that food.
  4. However, in 2.5-3 hours post meal, the levels of insulin drop off, and the hormone will no longer inhibit your ability to access the carbohydrates 

So again, eat at least 3 hours prior to competition.  Well, at least now we know it was not my fault for being terribly slow was entirely insulin's fault.

How to Eat Carbs During
During an endurance activity, muscle breaks down carbohydrates at a rate of about 1g per minute.  Thus, consuming 30 g of carbs every 30 minutes is ideal.  Great sources of carbohydrates include sports drinks and power gels.  The reason why these sources are so effective is because they are composed of simple sugars that are quickly absorbed and subsequently utilized.  This is the one time in your life where sugar is the best thing you can possibly have, so take advantage of it.  It is important to stay away from fibre and fat as they both slow intestinal absorption of food, while fibre encourages water retention in the intestinal tract.

It is important to note that after your race begins, you should wait 30-40 minutes prior to ingesting any carbohydrate containing foods or liquids.  The reason for this, once again, is related to my arch-nemesis: insulin.  Essentially, if you eat too soon, your body will act as if it is in a fed state, and thus be reluctant to release glycogen and fat stores.  

The key things to remember from this article include:
  • Exercise to exhaustion and then carboload to maximize glycogen stores for competition
  • Do not eat within 3 hours of competition
  • After the first 30-40 minutes, consume 30g of carbs every 30 minutes during activity
  • A delicious greasy pizza consumed 30 minutes before training may feel right at the time, but apparently science says it is quite the opposite
There will be more to come on nutrition and athletic performance, next week I will discuss the importance of protein (probably).


 Burke L.M.  et. al. 2006. Energy and carbohydrate for training and recovery. J Sports Sci. 24:675–85. 

 Meschino, J.,  2010. Nutritional Aspects of Athletic Performance. Pages: 1-10