Pre-tour favourite Alexandre Vinokourov failed a doping test, Christian Moreni tested positive for elevated testosterone levels, and Michael Rassmussen has been sacked by his team after he missed two out-of-competition drugs tests.

This was the last thing the tour wanted after last year's tour winner, Floyd Landis, tested positive for testosterone.

However, cycling is not on its own. At the last Olympic G ames, in Athens, three gold medals were stripped from their winners, and there were 24 doping violations in total, double the previous highest number.

So, is the increased number positive drugs tests indicative of more cheaters in sport, or because of the greater co-ordination and administration of anti-doping tests?

It is most likely a combination of the two. The ever-increasing media coverage and financial rewards for our sporting champions is a major contributing factor behind increased doping. However, don't under-estimate the role of the athlete's support staff who also are likely to benefit from their client's successes.

But scientific research continues to improve our knowledge of banned substances and the physiological markers that indicate their use, allowing us to provide more accurate drug testing.

Furthermore, the World Anti-Doping Agency (WADA) has developed a more co-ordinated testing regime that includes testing out of competition, and has become more stringent with athletes who miss or attempt fraudulent drug tests.

There are six major categories of doping (anabolic agents, blood doping, peptide hormones, stimulants, diuretics, and narcotic analgesics), all of which give specific short-term advantages to certain attributes crucial to success in sport, such as endurance, strength, alertness or aggression.

In the Tour de France, blood doping, anabolic agents and narcotic analgesics are most prevalent because of the high endurance demands and limited
recovery time.

Blood doping involves injecting red blood cells or related products that increases the oxygen carrying capacity of the blood and, therefore, increases the athlete's endurance. This blood doping can be detectable. However, a common practice is to remove and store up to a litre of the athlete's own blood a few weeks prior to competition, allow the body to replace the lost blood and then re-infuse the stored blood into the athlete's body just prior to competition. This method is more difficult to discern.

Some would argue that the use of drugs is no different to the use of other performance-enhancing supplements. What is the difference between using these banned substances and sports drinks or supplements that contain carbohydrates, proteins or electrolytes?

In our laboratory at the University of Hull, we continually carry out research into the effects of supplements such as caffeine, sodium bicarbonate, oxygenated water and glycerol, and we commonly observe improvements in performance.

However, as long as the correct dosage is administered, these agents are not banned by WADA, and are, therefore, legal. The difference between these agents are that banned substances are considered to be detrimental to the long-term health and well-being of the athlete.

For example, blood doping can potentially cause a stroke or heart attack, or transmit blood-borne diseases such as HIV and hepatitis. In addition, anabolic agents can cause cardiovascular problems, liver damage and also psychological changes.

So, why then do these cyclists bother to take drugs given the established side-effects and heightened chances of getting caught out by WADA and other agencies?

Well, there are of course, hundreds of thousands of pounds at stake for the winner, but many will need a helping hand just to complete the race.

The Tour de France is widely acknowledged as the hardest race
in the world. It covers 2,200 miles
in 20 stages over 22 days. The average speed of the cyclists is approximately 25 miles per hour and the riders expend, on average, 5,900 calories a day, up to 10,000 per day on a mountain stage.

Compare this to a marathon, where we run 26 miles in a few hours, hit the "brick wall" for the last hour and feel the pain for the next three days. Imagine trying to do this every day for more than three weeks, with no time to recover in between stages or to take on board sufficient calories to restore our energy levels. This is a major factor why the Tour is associated with drug use.

Historians point out that drugs have probably been used to enhance sporting performance for more than 2,000 years, so it is unlikely the problem will ever go away. Unfortunately, as the science of detection advances, so, too, does the science of masking the evidence of drug abuse.

Regardless of how sophisticated the drug detection becomes, the fact remains that performance-enhancing drugs cause health risks.

The race to beat the drug tests is a race nobody wins. With those committed to the detection of drugs competing with those who try to mask their use, it will be interesting to see which side wins before the start of the 2008 Tour de France.


Ric Lovell is a doctor of sports physiology at Hull University. Besides his research, he is a sports science consultant to professional athletes of both national and international standard.