Though the results of the B sample have yet to be confirmed, Shoaib Akhtar and Mohammad Asif testing positive for Nandrolone is just another peek at the dirty subterranean world of professional sport. With cricket only recently getting tough on drugs, you can rest assured that they won't be the last big names to be hauled up.

What, though, is Nandrolone, and why have so many elite athletes tested positive for it in recent years? According to the International Union of Pure and Applied Chemistry (IUPAC) system of nomenclature, the anabolic steroid has the name 17b-hydroxy-19-nor-4-andro-sten-3-one, and can occur naturally in the body, albeit in minute quantities. Structurally, it's very similar to Testosterone, the male hormone that was recently the buzz word in sports bulletins after Floyd Landis, the Tour de France winner, tested positive for excessive levels.

Like Testosterone and Creatine, the amino acid that Juventus's football team were alleged to use regularly in the 1990s, Nandrolone too increases muscle mass. It can also produce the same side-effects, like overly aggressive behaviour, as testosterone. Clinical experiments have been conducted in the past to see its efficacy in the treatment of HIV-affected men and also for other diseases that cause muscle wastage.

The tests for Nandrolone, which involve urine samples, are considered positive if the level exceeds 2 nano grams per ml, the limit set by the International Olympic Committee which is considered the maximum possible in natural cases. Most positive tests have involved athletes with levels hundreds of times above normal.

Those caught in the past have included Linford Christie, Olympic 100m champion in 1996, and Petr Korda, the Czech tennis player. Football, though, has had to endure the most scandal, with Jaap Stam, Edgar Davids, Frank de Boer (The Netherlands), Fernando Couto (Portugal) and Josep Guardiola (Spain) all having served bans for nandrolone use.

The testing procedures have not been without controversy though. Athletes who have been caught have often cited the use of Creatine and the consumption of protein shakes as the reason for positive tests. An Aberdeen University study suggests that they may have a point. According to that, consumption of dietary supplements in conjunction with heavy physical training can result in the athlete returning a positive test for Nandrolone. As with many drugs, including THG that was involved in the infamous BALCO case, our knowledge is far from comprehensive. And as long as that remains the case, the protestations of innocence from those caught may just have a ring of truth to them.