The Science Behind Blood Doping
First published in NZ triathlon and Multisport Magazine 2012
As I sit down to right this article we are amidst the fallout from the Armstrong doping scandal. Since this started coming out I have had a lot of questions about the how’s and whys behind doping and detection. There have been an enormous number of articles, blogs and interviews talking about the key figures and sums of money behind the doping scandal which make for some interesting reading.
This article in no way supports the practice of blood doping. My aim is to provide some education and clarity around what is very dark and sometimes confusing topic. I want to explore some of the physiology behind the practice of blood doping, detection and the avoidance of detection.
Red blood cells are the oxygen carries of the body, transporting oxygen from the lungs through the blood vessels to the muscles that require it to produce energy for movement. The average adult male has approximately 6 litres of blood pumping around their body.
During endurance training one of the main adaptations that occurs is an increase in blood volume, both red cells and plasma volume. This adaptation is kick started when the kidneys experience hypoxia (a decreased oxygen availability) and are stimulated to release EPO. Now I am sure everyone has heard of the drug EPO, and some maybe shocked to hear that we all have EPO in our system.
EPO is the abbreviation for erythropoietin which is a naturally occurring growth hormone. When released from the kidneys, EPO stimulates the bone marrow to produce new red blood cells and at the end of the day more blood results in an athlete being able to race harder for longer (i.e. improves fitness).
So the search for more blood and an increase in performance has lead athletes to pursue different legal (altitude and heat training) and illegal (artificial EPO and blood transfusions) means of getting a competitive edge. Blood doping was banned by the International Olympic Committee in 1985, however at the time there was no test designed to detect it.
This battle of the testers ‘keeping up’ with the dopers is something that still rages today.
Types of blood doping
Originally blood doping referred to the transfusion of blood into an athlete. The first known case of blood doping occurred at the 1980 Olympics when a Finish runner used a blood transfusion to win a silver and bronze medal in the 10 and 5 km events respectively. By withdrawing and freezing approximately 1 litre of blood from an athlete (just like giving a blood donation) the athlete is able to then naturally restore that lost blood overtime.
Then before a big race this blood can be thawed out and re-infused giving the athlete a ‘super-human’ amount of blood to supply their muscles during exercise. This supply of blood can come from the athlete as described above, however the repeated practice of this impacts on the athletes training and recovery during the ‘donation’ phase. So to overcome this, blood can be with-drawn from another individual with the same blood type, just like what happens with a blood transfusion following an injury from a severe accident or surgery. The risk of infection and blood type incompatibility following the infusion of others blood is high so this method can have some serious health effect.
In the late 80’s the availability of recombinant DNA technology allowed a synthetic EPO to be created on mass for the treatment of patients suffering from anemia (low red blood cell volume) as a result of kidney failure or chemotherapy treatment.
This pharmaceutical EPO was extremely hard to detect as it is nearly identical to the natural hormone and was soon being used across numerous endurance sports replacing the older transfusion method.
By injecting EPO there is a large stimulus sent to the bone marrow to produce new red blood cells. The EPO levels in the blood decrease relativity quickly making it hard to detect the actual drug, but it’s effect of producing more red blood cells has a longer last effect.
The average life cycle of a red blood cell is 120 days, therefore following an EPO injection the influx of new red blood cells and the elevated level of blood volume within the circulation will last a number of weeks. Because EPO only increases the red blood cells, the blood becomes thick and hard to circulate. This causes problems such as embolisms (blocking of blood vessels with clots), leading to heart attacks, strokes and death in otherwise healthy athletes. To combat this plasma volume expanders are also required to boost up the fluid component of blood, so everything keeps circulating freely.
So how do you detect if someone has withdrawn their own or someone else’s blood and put it back into them? Or how do you know if someone is using a pharmaceutical EPO to stimulate their body to produce more red blood cells?
One of the first tests used to catch blood dopers was to measure their hematocrit. Hematocrit is the percentage of red blood cells compared to the amount of plasma they have.
A hematocrit over 50% for men and 46% for woman have been set as normal levels. This test can be by-passed quite easily using plasma volume expanders (which are also banned) to give an individual more plasma to ‘dilute’ the red blood cells and therefore bring their hematocrit under 50%. Alternatively if an individual is dehydrated and has lost plasma volume through sweating then it can increase hematocrit and push them over the limit when they may in fact be ‘clean’. So while this test was a good starting point it had some major flaws.
In a ‘clean’ athlete the age of their red blood cell population fits a normal distribution with numerous cells ranging from 0-120 days old. As mentioned above when EPO is injected there is a large influx of red blood cells produced by the bone marrow and all of these red blood cells will be the same ‘age’. This large population of red blood cells of the same age will over represent a particular age bracket indicating EPO usage at a specific time.
In 2000 a test was developed that detected EPO present in an athlete’s urine. The introduction of this test made mass regular testing much easier and the combination of blood and urine tests resulted in a large number of doping cases brought against athletes.
This new improved testing regime led many athletes to revert back to the original blood transfusion method to avoid detection. However, with the advances in testing technology for blood transfusions many athletes were caught using that method as well. By analysing microscopic markers on the surface of red blood cells scientists can now tell if there are cells from more than one individual within an athlete’s circulation.
Also the use of a technique similar to EPO detection looking at the mature vs. immature red blood cells can show if an athlete has had their own blood re-infused. Even more recently the detection of plasticizers in blood has been used in some high profile doping cases. Plasticizers are additives contained in IV bags that are used to store blood and they help keep the bloods fluid consistency while it is stored. When the blood (along with the plasticizers) is re-infused into the athlete they can be detected and used as evidence of blood doping.
While the anti-doping organisations do their best to keep up with the influx of new methods of illegal performance enhancers they can only test for things they know about and in a legal setting their testing protocols have to be ‘bullet proof’. This makes it very hard for the testers to keep up the dopers. Hopefully some good can come out of the Armstrong doping scandal and a sport that has an engrained doping culture can move towards a cleaner future.
Sport Scientist and Performance Coach
Powers and Howley., 2007, Exercise Physiology, sixth edition, McGraw Hill
Sytkowski, 2006.,Erythropoietin, John Wileys & Sons
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