The World Anti-Doping Agency has followed the UCI’s crackdown on carbon monoxide rebreathing and added the use of the gas as a performance-enhancer to its prohibited list, starting from 2026.
The non-diagnostic use has been added to the list, as “it can increase erythropoiesis under certain conditions,” WADA has stated.
Erythropoiesis, or the production of oxygen-carrying red blood cells, can be stimulated by the inhalation of carbon monoxide. However, in sufficient doses, the inhalation of this gas can be fatal, raising safety fears about riders potentially risking their health for performance gains.
This stimulates the type of hypoxia, or lack of oxygen, that would occur at high altitude levels. Training camps in high altitude have become standard for professional cyclists, as hypoxic exercise improves the body’s ability to use oxygen during exercise.
The gas can still be used as a diagnostic tool. For example, it could be used during altitude camp to track a rider’s progress over a block of training, as it provides an accurate means of measuring haemoglobin.
“Carbon monoxide for diagnostic purposes, such as total haemoglobin mass measurements or the determination of pulmonary diffusion capacity, is not prohibited,” stated WADA in the summary of major modifications to the 2026 Prohibited List.
“The current wording was chosen to differentiate between illicit use and the intake resulting from natural combustion processes (e.g. smoking), the environment (e.g. exhaust gases) or diagnostic procedures.”
This follows controversy after a report by the Escape Collective website, which stated that UAE Team Emirates, Visma-Lease a Bike, and Israel-Premier Tech allegedly used carbon monoxide during the 2024 Tour de France.
The teams of Jonas Vingegaard and Tadej Pogačar confirmed that they had access to the equipment for testing, but any alternative use has not been proven.
Both Pogačar and Vingegaard admitted at the 2024 Tour de France that they had previously used carbon monoxide rebreathers, but within the context of testing.
“It’s to measure how much haemoglobin you have in your blood. There is nothing suspicious about it,” said Jonas Vingegaard.
“They [the doctors] say that they send something into the lungs that is similar to smoking a cigarette. We measure the day we get to our high-altitude camp and then [on] the day we go back down. Then we see the difference in how much haemoglobin is built up. There is nothing more to it.”
Despite the teams denying its exploitation for direct performance-enhancing gain, former DSM-Firmenich PostNL climber Romain Bardet believed it could be used to enhance performance.
“We see the studies. Anything is possible. I have never heard of anything but at the same time, I would not be surprised.
“There is so much research being done with the idea of optimising performance. Ten years ago, there were lots of promises about altitude. Everyone was getting involved, it was a bit of a panacea. We know exactly where it can take us.
“It is not surprising that there are certain researchers, certain teams, certain cyclists who are looking elsewhere. There will always be the desire to seek competitive advantages.”
WADA’s statement follows the UCI in February announcing a ban on the “repeated inhalation” of carbon monoxide “outside a medical facility”, claiming that the controversial method of measuring an athlete’s haemoglobin can cause chronic health problems if used frequently.
Cycling’s governing body proposed its plans for the ban in December last year, and the new regulation means that teams and riders are forbidden from being in the possession of commercially available carbon monoxide rebreathing devices connected to oxygen and carbon monoxide cylinders.
5 thoughts on “WADA to ban carbon monoxide rebreathers as a performance aid from 2026”
Completely unworkable. It’ll
Completely unworkable. It’ll be near impossible to obtain test samples for this in practice. And even if they could get test samples, there’ll be easy excuses available for any ‘positive’ results.
Been brought in mostly to sate online hysteria.
CO rebreathing is a way athletes with little money can get on a level footing with athletes with vast resources, who can afford to spend the off-season and a quarter or more of pre-season living high up at altitude in the mountains. So, banning this just hands the advantage back to the big, rich teams. (If such a ban has any effect).
Paul J wrote:
I don’t think they’re intending to test for it; as you say, it would presumably be impossible to differentiate between deliberately inhaled carbon monoxide and that inhaled from riding in busy traffic (although I was quite amused by them also saying that they wanted to differentiate between carbon monoxide arising from “natural combustion processes, e.g. smoking” – if Pog or Jonas try to claim their levels were due to having forty Camels the night before that might raise a few eyebrows).
As the article says, “the new regulation means that teams and riders are forbidden from being in the possession of commercially available carbon monoxide rebreathing devices connected to oxygen and carbon monoxide cylinders.” They aim to police this by outlawing the equipment rather than going after blood tests, although unless they have the budget to carry out raids on preseason training camps et cetera not quite sure how many they would catch.
Rendel Harris wrote:
Funnily enough, smoking was known to have this benefit – if used correctly. 😉 (Short-term benefit – obviously beyond that it’s a disadvantage).
Well no one using CO rebreathing has ever brought the equipment to races. The CO rebreathing itself noticeably _reduces_ performance in the days immediately after. Some of your haemoglobin is bound to CO, and unavailable for oxygen transport, for up to ~1 week (decaying rate). It is the bodies response to this subtle, chronic (days at least) hypoxia that this CO rebreathing is seeking to stimulate after all. No one is going to be doing this during a race, or even a week before a race. They’ll be doing this 1 or 2 months beforehand. The extra blood cells the body hopefully produces last for 2 to 3 months.
So yes, how will they police this? The testers doing off-season testing, getting samples, are not going to be searching the athletes’ hotel or home for equipment – they don’t have that authority! Nor are those testers generally certified phlebotomists – so they can’t take blood samples either!
They won’t get the blood samples. They won’t be able to do searches. It’s a complete joke of a rule.
All this does is to take one (cheaper) option for the stimulation of erythropoiesis through chronic, mild hypoxia off the table. Leaving only the much much more expensive option (and very limited in terms of hotel rooms – there is literally *1* hotel at altitude in the EU that is useable for cyclists in the winter, and it isn’t that big; though it has expanded). Which only the biggest, richest teams can afford.
How is that good for the sport?
I think this brings into
I think this brings into focus a broader question. What things should be allowed that effectively stimulate a similar physiological response to “normal training”.
Thats effectively what many things that are considered dodgy do. They don’t give you an out and out advantage but they make getting from A to B faster or easier.
As you say, what about the smaller teams that don’t have the budgets to optimise every little aspect of their riders lives and training.
Good points, should anything
Good points, should anything other than conventional training be allowed? Looks incredibly hard to define conventional objectively nevermind police.