LEEDS, England -- Doping has been an unfortunate part of the Tour de France since its inception in 1903. Instead of today's high-tech performance enhancers like blood-booster EPO, riders juiced up on wine and cocaine, even strychnine, to get a lift in the race.
As the sport went prime-time and grew more competitive and lucrative, the crackdown on doping cheats also intensified -- leading to the eventual dethroning of seven-time champ Lance Armstrong, the most famous rider of a tainted era.
Anti-doping testing was introduced at the Tour in the 1960s but did not prevent the death of British rider Tom Simpson on the slopes of the Mont Ventoux in 1967 after he used a lethal cocktail of amphetamines and alcohol.
Here are five things to know about doping before the race starts on Saturday:
THERAPEUTIC USE EXEMPTIONS
Reigning Tour champion Chris Froome drew controversy after a UCI medical supervisor authorized his use of a doctor's note in order to take a corticosteroid to fight a chest infection during the Tour de Romandie this year. Cyclists who suffer from illness can, in some cases, be given such a Therapeutic Use Exemption to use otherwise-banned medication.
Because of that incident, the governing body's TUE panel -- not just a single UCI doctor -- will from now on examine all such exemptions, the head of cycling's governing body Brian Cookson said Friday, reasoning that "maybe they're all of a potentially controversial nature."
Cookson also said a key lesson for today's competitors from Armstrong's era was that sooner or later, "We will catch you." While he said he couldn't guarantee that new doping cases won't come to light at this Tour, "the radar is being lowered all the time."
In a meeting with two reporters, Cookson said the science and technology involved in catching drugs cheats are improving and sport authorities continue to enhance their anti-doping procedures.
"I think we are closer to the cheats than we have ever been," he said.
Two riders who were expected to compete in the Tour were suspended by their teams before the race. Daryl Impey of South Africa, who last year became the first African to wear the leader's yellow jersey, failed a drugs test in February and was removed from the Orica-GreenEdge lineup after the Australian team was notified of the result.
Involved in a case dating back to 2011, Roman Kreuziger -- a key climbing lieutenant of Alberto Contador on Tinkoff-Saxo -- was dropped by the team because of anomalies in his biological passport detected in 2011 and 2012. The Czech rider, who won the Amstel Gold Race last year, was with Kazakh team Astana at the time. Kreuziger denies any wrongdoing.
WHO'S HANDLING THE TESTING?
The UCI is again teaming up with the French anti-doping agency AFLD to test riders on the Tour. Blood checks will be carried out on all participants before Saturday's first leg from Leeds to Harrogate, the first of three stages in Britain. The British anti-doping agency will also be involved, sharing intelligence and information about the potential cheats.
AFLD will use data from the UCI's biological passport program to target possible cheats, but also information from a special French police unit specialized in the fight against doping.
Some samples will also be kept to be tested in the future -- in expectation that detection methods may improve in the future.
No riders tested positive for doping during last year's race, where 622 samples were collected.
Four well-known doping offenders will be at the start line in Leeds:
• Alberto Contador: The joint favorite, with Froome, to win this year's race, Contador was stripped of the 2010 Tour title and was suspended for two years after testing positive for clenbuterol in the final week of the race that year. Contador claimed he ate a contaminated steak bought in Spain.
• Alejandro Valverde: Fellow Spaniard Valverde was handed a two-year suspension in 2010 for his involvement in the Operation Puerto doping plot, which ensnared dozens of riders over secretly stored blood bags. The 34-year-old Valverde is leading Team Movistar, and is regarded as a potential Top-5 finisher.
• Rui Costa: The Portuguese world champion with the Lampre squad tested positive for stimulant methylhexanamine in 2010 following his victory in the national time trial championship. He was given a one-year ban, which was reduced to five months on appeal. He won his third consecutive Tour de Suisse last month.
• Frank Schleck: Schleck, the elder brother of 2010 Tour champion Andy Schleck, missed out on last year's Tour because of a one-year suspension for a positive test for a diuretic during the 2012 race. Last month, the 34-year-old Schleck claimed his fifth Luxembourg champion title.
NOT MILLAR'S TIME
One of the most outspoken voices against doping, David Millar, will be conspicuously absent this year. The Scottish veteran was denied the chance to compete with the Garmin-Sharp team, which cited his ill health for keeping him out of the roster this year.
Millar, 37, completed a two-year ban in 2006 after confessing that he used the blood-booster EPO, then joined the World Anti-Doping Agency's athlete committee.