Illegal readings, innocent explanations, and a decade-long steroids controversy

Nandrolone is a steroid, a substance that can give sportsmen and women an illegal advantage in terms of strength and endurance. It is on the International Olympic Committee's (IOC) banned list, and those testing positive for it face a variety of punishments depending on which sport they play.

Nandrolone is a steroid, a substance that can give sportsmen and women an illegal advantage in terms of strength and endurance. It is on the International Olympic Committee's (IOC) banned list, and those testing positive for it face a variety of punishments depending on which sport they play.

Greg Rusedski, who confirmed last night that he had tested positive for a low level of nandrolone, faces suspension but the duration is open to debate. Tennis has not yet signed up to the World Anti-Doping Agency's code, due to be operational before this year's Olympic Games, which would make the punishment for such an offence a two-year ban, as it already is in other sports such as athletics.

While the Lawn Tennis Association struggles to come to terms with the repercussions of the latest disclosure, Britain's governing body for athletics can count itself something of a veteran in the nandrolone field, having seen a rash of positive findings in recent years involving high-profile competitors such as the 1992 Olympic 100m champion Linford Christie, the 1996 Olympic 400m relay silver medallist Mark Richardson and the 1998 European 200m champion Dougie Walker.

Other sporting figures to have tested positive for nandrolone include the former Australian Open tennis champion Petr Korda, at Wimbledon in 1998, and Birmingham City's French international World Cup winner Christophe Dugarry.

The sudden outbreak of positive tests for nandrolone among British athletes in the late 1990s left UK Athletics bewildered. All athletes involved vehemently denied taking performance-enhancing drugs, just as Rusedski has done. Cynics might observe: "They would, wouldn't they?"

But research into a problem which briefly tipped British athletics into a state of panic provided a conclusion that made this apparent outbreak of mass-cheating more palatable.

Initial studies by a research team at Aberdeen University and, independently, by Fifa, the world football body, indicated that nandrolone levels could rise to punishable levels through strenuous exercise.

Then another strand of research indicated a cause which subsequent study by an IOC-accredited laboratory has confirmed - that nutritional supplements labelled as being clear of any adverse substances were, in some cases, contaminated with nandrolone at the point of manufacture.

Like all steroids, nandrolone has side-effects - prolonged use causes liver and heart damage. Women may develop facial hair and men can suffer from baldness and impotence. It was put on the IOC banned list in 1975.