There are several types of performance-enhancing drug that an athlete can use.
There are several types of performance-enhancing drug that an athlete can use.

There are several types of drug that an athlete can use to enhance his or her performance.
Some of these drugs are banned by law and some are legally available on prescription, but they are all prohibited by sporting regulations. (When we use the word 'illegal', we mean it in this sense.)
The name of this process is slightly misleading: it should not be confused with 'doping' in general. Blood doping may or may not involve a drug. It is the process of artificially increasing the concentration of red blood cells in the blood. More red cells result in more oxygenated blood reaching the muscles.
The red blood cell level, as a percentage of the blood, is called haematocrit. In men the normal haematocrit range is 40-54 per cent, and in women it is 37-47 per cent. In cycling, a sport prone to blood doping, authorities now test haematocrit levels and ban those above 50%. Athletes with naturally high levels must prove it by being tested over several months.
There are two main methods of blood doping. An athlete could inject extra red cells, either from a donor or previously harvested from the athlete's own blood, or take a drug to boost their production.
A blood transfusion is dangerous to attempt during a competition because of the difficulty of smuggling in frozen blood and (sometimes unsterilised) medical equipment and using them unsupervised.
The drug most commonly used to boost red cell production is erythropoietin. Erythropoietin can cause heart attacks or blood clotting if used excessively, and may also damage the immune system (the white blood cells).
WADA, the World Anti-Doping Agency, is an independent body formed by the International Olympic Committee in 1999 with the responsibility of fighting drug-taking in sport and ensuring impartiality and rigour in drug testing. It's WADA that maintains the list of banned substances. It also conducts drug testing, provides assistance to countries' own anti-doping programmes, and funds research.
The World Anti-Doping Code was introduced in 2004 to coincide with the Olympic Games in Athens. The Code standardises the rules and regulations governing doping across all organised sports.
Countries that follow the Code have their own regulatory bodies. In the UK, anti-doping measures are controlled by UK Sport. The USA has the United States Anti-Doping Agency, USADA.
The synthetic steroid THG (tetrahydrogestrinone) came to prominence in the summer of 2004 after one coach 'blew the whistle'. He sent a sample of the drug to the United States Anti-Doping Agency, exposing its use.
THG had never been spotted before because it was a new synthetic drug, designed to be undetectable. With a sample, though, the Anti-Doping Agency was able to develop a test for the drug - and many prominent sports players and athletes were engulfed in the subsequent scandal.
The whistle-blowing coach in question is called Trevor Graham. In an interview he said: "As a coach it seemed the right thing to do at the time and it still does."
Is it the right thing to report a fellow competitor for cheating? If you are not cheating yourself, then it could be considered reasonable to report someone who is.
Because it is obviously in a competitor's interests to disqualify a rival, authorities have to take the source of the accusations into account.
It is likely that drugs manufacturers will continue to be steps ahead of the regulators. It is possible, even likely, that there are other 'undetectable' drugs in use. Drug investigators and coaches alike are pragmatic about the fact.
As genetic therapy techniques develop, the opportunity to cheat begins to look limitless. Future developments in performance-enhancing substances may include:
The nature of genetic therapy treatments means they will probably be almost impossible to detect.
This is one of the points used in arguments for the legalisation of drugs.
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