The doping agent Aicar, a muscle-enhancing and fat-burning drug, is believed to be back in the professional peloton at the Tour de France 2019, with anti-doping agencies put on alert after tip-offs from prominent, yet anonymous, figures within the world of cycling.
Aicar is produced naturally by the body, which makes it hard to test for artificial forms. The substance causes an increase in the body's red blood cells and increases fat and carbohydrate burning.
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Rumours have even been circulating that one team within the peloton are giving their riders Aicar in their bidons, sometimes without the riders's knowledge.
These claims have been made in Dutch newspaper De Telegraaf, with a WADA-associated (World Anti Doping Agency) lab confirming it was urged by an individual involved in anti-doping at the start of June to accelerate its investigation into Aicar, as a number of people believed the substance was being used by several riders currently taking part in this year's Tour de France.
Aicar is currently available to order over the internet, with 5mg costing around €70. The powder form is still in it's experimental phase, meaning there are many side-effects and risks associated with it.
Professor Peter van Eenoo, who is the director of a Wada-affiliated lab in Ghent, Belgium, said: "I am not surprised that Aicar is used in cycling. It can also be no coincidence that a few WADA laboratories have recently been warned about Aicar and that murmurs are now coming from cycling.
"A request has been made to make greater efforts to track down Aicar. We had put research into this product on the back burner because we no longer saw it as a major problem."
In a lab test on mice it was found that Aicar had the ability to increase endurance capacity by 68 per cent. It has also been found that Aicar works well when combined with GW1516, which has similar effects, with RusVelo rider Valery Kaykov failing an anti-doping test after coming up positive for the substance in 2013.
Douwe de Boer, a doping expert who checks the biological passports for various professional cycling teams, says he's not surprised to hear of rumours that Aicar is being used again, calling it the perfect doping agent because "it's a natural substance, it's difficult to detect."
"You also have the option of tracing through the parameter of fat in your blood for the biological passport," he continued, "but this is quite difficult. The danger that cyclists are taking it is constantly lurking. Looking for the limits is part of the top sport. Some adhere to the doping list, others also search for limits in the doping list."
In Van Eenoo's lab, they check Aicar in a similar way to how they check testerone levels, by testing an individual's urine. He says the level of Aicar in a person's body can fluctuate a lot, and some people can have naturally occurring high values meaning the acceptable threshold level is also quite high.
"The laboratories can only indicate users of this product to a very limited extent. Only if the value really swings out of the pan can we continue to investigate," Van Eenoo said.
However, Van Eenoo admits that it hasn't yet been proven to what extent the substance has a direct effect on the performance of top athletes, adding you have to take quite large quantities before it can have any effect.
The head coach of Jumbo-Visma, Merijn Zeeman, told De Telegraaf that he is surprised to hear of Aicar's revival, saying the fact his team have been able to compete, taking three stages and holding the yellow jersey so far in this year's Tour, has been because he believed the peloton was riding clean at the moment.
"It is precisely because we are able to compete again this year that we have the feeling that there is currently quite a pure race," he said. "I don't know about these murmurs surrounding Aicar. Although the Austrian Operation Aderlass recently demonstrated that doping has not yet been completely banned from the pack. "
