What is blood doping, will it affect the Winter Olympics 2018 and what’s the difference between EPO and blood transfusions?
The Pyeongchang Winter Olympics has been hit by a doping scandal days before the opening ceremony
SHOCKING revelations appear to show widespread practice of blood doping among Winter Olympics medallists.
But what is the illegal performance enhancer, will it affect this year's Games and what's the difference between EPO and blood transfusions?
What is blood doping?
Blood doping is defined by the World Anti-Doping Agency as the misuse of techniques and or substances to increase ones red blood cell count.
Injecting your own, or another person's blood prior to performance can increase stamina and performance.
All types of blood doping are prohibited.
Will it affect the Winter Olympics 2018?
Blood doping has already been revealed as a major issue around the Winter Olympics in Pyeongchang in South Korea, after secret papers revealed that up to a third of all medallists provided dodgy test results.
Hundreds of skiers escaped bans despite recording unusual blood test scores, according to a database leaked to The Sunday Times and German broadcaster ARD.
Analysis of more than 10,000 blood tests from 2,000 winters sports stars showed that about a third of all medals won in the Olympics and World Championships since 2011 recorded suspicious tests.
Russia, which has been banned from competing under its own flag at this year's Olympics, tops the list of cheating countries.
The secret data also reveals that more than 50 South Korean skiers on the qualification list recorded unusual blood test scores, suggesting they could have cheated in the past but escaped punishment.
Coming days before the opening ceremony in Pyeonchang, the findings have rocked the championships.
But the games are likely to go ahead as expected, after the World Anti-Doping Agency saying it was "more than satisfied" with its anti-doping efforts.
What's the difference between EPO and blood transfusions?
There are a number of widely known substances or methods used for blood doping, including erythropoietin (EPO) and blood transfusions.
EPO is a peptide hormone that is produced naturally by the human body but that can be injected to create unnaturally high levels of red blood cells.
It's released from the kidneys and acts on the bone marrow to stimulate red blood cell production.
Blood transfusions involve injecting blood back into your body.
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There are two types - autologous, where the blood donor and transfusion recipient are the same - and homologous, where the blood is transfused into someone other than the donor.
The process involve withdrawing between one to four pints of blood several weeks before the competition, and refrigerated or frozen depending on the method.
The blood is then thawed and reinjected into the recipient between one and seven days before a high-endurance event.
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