In the same week that Tadej Pogačar’s UAE Team Emirates squad claimed that it is no longer using the controversial method of carbon monoxide rebreathing to test riders’ progress during altitude training camps, the UCI has announced that it will propose a ban on the use of the toxic gas on “medical grounds”, due to the risk of both immediate and long-term health side effects when inhaled repeatedly for performance enhancing purposes.
However, cycling’s governing body says that carbon monoxide’s use in a “strict” medical setting for testing, such as those carried out at training camps by UAE Team Emirates and Jonas Vingegaard’s Visma-Lease a Bike team, would remain authorised if a ban is put in place.
In a statement released on Thursday morning, the UCI announced that it will propose to its management committee that the use of carbon monoxide (CO) by riders should be banned, with a decision expected to be made at the governing body’s next meeting in Arras, France, at the end of January.
The proposed ban comes just over two weeks after UCI president David Lappartient publicly called for the World Anti-Doping Agency (WADA) to “take a position” on the toxic gas’s use in sport, while requesting that teams and riders avoid “repeated CO inhalation”.
The controversial use of carbon monoxide in the pro peloton has been in the news since Escape Collective revealed during this year’s Tour de France that UAE Team Emirates, Visma-Lease a Bike, and Israel-Premier Tech have access to a CO rebreather to test blood values.
Providing an accurate means of measuring key blood values such as haemoglobin (a protein that facilities the movement of oxygen in red blood cells), several pro squads then confirmed that they use CO rebreathers to track their riders’ progress during red blood cell boosting altitude training camps.
Both Tadej Pogačar and Jonas Vingegaard admitted at the Tour that they had previously used carbon monoxide rebreathers, with Pogačar even dismissing the practice as a “pretty simple test” and claiming he’d never actually completed it.
However, despite not breaking any current anti-doping rules, those very same carbon monoxide rebreathers also allow for precise dosing of the gas into the lungs, which could potentially assist riders’ bodies in producing more red blood cells and improve their aerobic capacity, enhancing their performance artificially – an alternative use of the equipment which has not yet been proven to have been employed by any WorldTour teams.
At the start of November, veteran grand tour contender Romain Bardet suggested that the advent of carbon monoxide use in the peloton could explain the dramatic jump in form of certain riders over the past 18 months, pointing out that “there will always be the desire to seek competitive advantages” within the pro peloton.
But later that month, two-time Tour de France winner Jonas Vingegaard downplayed the potential health effects of the much-discussed method, claiming it is akin to “smoking one cigarette” and noting that “there are a lot of people smoking cigarettes every day”.
The Visma-Lease a Bike rider also claimed he was unaware that the method could be “misused” for performance enhancement purposes, stating that he will refrain from using the gas if it is banned by the UCI and WADA.

(ASO/Charly Lopez)
And it’s that “misuse” which the UCI has focused on, as they prepare to ban the gas unless it is deployed in a strict controlled testing environment.
In a statement released today, the governing body said: “Carbon monoxide is a toxic, odourless gas that is often a cause of household accidents. Inhaled in low doses and under strict safety conditions, the gas is used in medicine as a tracer to measure the pulmonary diffusion of oxygen or of the total haemoglobin mass.
“However, when inhaled repeatedly in non-medical conditions, it can cause side effects such as headaches, fatigue, nausea, vomiting, chest pain, breathing difficulties, and even loss of consciousness.
“The UCI considers that these health side effects, and the complete lack of knowledge about the long-term effects of repeated inhalation of carbon monoxide, justify a ban on the use of this gas due to medical reasons.
“Its use in a medical setting, by qualified medical personnel, and within the strict context of assessing total haemoglobin mass, would, however, remain authorised.”

(ASO/Charly Lopez)
Any proposed ban, either for performance enhancing or testing purposes, will apparently have no effect on UAE Team Emirates, however, after the team’s performance co-ordinator Jeroen Swart confirmed this week that the squad has stopped using carbon monoxide rebreathing after finishing an 18-month-long “process”.
“Carbon monoxide rebreathing is a technique that has already been validated for 20 years and has been used by climbers, endurance sportsmen and athletes around the world to measure haemoglobin mass when they go to altitude,” Swart said during UAE’s training camp in Spain this week.
“We’ve been very good with our altitude training camps in the last seven years. We feel that we’ve done a really good job in terms of the benefit, but there’s no way that you can quantify that clearly, other than measuring haemoglobin mass.
“So, two years ago, we decided to assess whether or not our riders were improving to our expectations. And so, it was an exercise that we conducted over 18 months and assessed the haemoglobin mass using carbon monoxide rebreathing which is a very standardised technique with very specific equipment.
“Actually, we finished that process now and our results show that our training camps are actually very well suited to the maximal adaptation for our riders which we see in the performances as well.
“So, we actually don’t need to do the tests any further. We don’t plan to do any more.”

(Zac Williams/SWpix.com)
After confirming the end of UAE’s dalliance with the controversial method, Swart then criticised what he deemed to be the “sensationalist” initial reporting on the issue in July, and dismissed the idea that teams would be using CO to artificially enhance their riders’ performances.
“I think it’s quite a sensationalist article that’s been published and speculating about using a technique that would be quite complicated and probably not something that I can see anybody actually doing,” he said of the alleged performance-enhancing benefits.
“It doesn’t come across as realistic. So, I think there’s a lot of sensation.”























9 thoughts on “UCI to ban use of carbon monoxide in pro cycling due to “health side effects” – but says controversial rebreathing method can still be used “in a medical setting” to test riders’ altitude training progress”
CO rebreathing seems like
CO rebreathing seems like something of a misnomer since breathing is defined as inhaling air not air mixed with CO. CO is only normally present in air at around 0.1ppm. Maybe it shoud be called CO suffocating??
Yes, sleep apnea produces
Yes, sleep apnea produces more CO… I’m not aware of any doping effect but what do I know.
I’m sure a closer look at some prescriptions might be more useful.
Except that air mixed with CO
Except that air mixed with CO is, er, air, since there’s no fixed definition of the constituent makeup of air – it’s just the mix of gases around us.
Well… constituent
True, but constituent percentages (or partial pressures) would be quite significant; I think I’d want to know before encountering an area with an anoxic atmosphere even if it’s just air… Apparently for carbon monoxide:
9 ppm (parts-per-million) is the maximum indoor safe carbon monoxide level over 8 hours
200 ppm or greater will cause physical symptoms and is fatal in hours
800 ppm of CO or greater in the air is fatal within minutes
(From here, slightly different numbers are also quoted elsewhere e.g. workplace exposure limits here).
Interestingly from here:
… so if you wanted to achieve all the training benefits of smoking without the carcinogens and vasoconstrictive effects you should aim somewhere below 100ppm!
Well I’m not suggesting that
Well I’m not suggesting that you’d generally want to breathe it. Only that the argument that ‘It’s not breathing because it’s not air if it has CO in it’ is distinctly dubious.
You’re misunderstanding why
You’re misunderstanding why it’s called “rebreathing”. The “rebreathing” aspect is because the CO/air mix is re-circulated for a period in a closed system. This ensures all the CO is absorbed – the measurement relies on the known dose of CO being fully bonded to haemoglobin in the blood.
So I don’t drink, because
So I don’t drink, because drinking is defined as drinking water, not water mixed with ethanol.
Hopefully it’ll still be
Hopefully it’ll still be allowed for recreational use.
This is one of the stupidest
This is one of the stupidest cycling controversies ever.
This is a test method that has existed for more than a hundred years, and has been a standard and often used test in sports physiology for at least many decades. The theorised performance benefits of chronic CO-induced hypoxia are via most of the same physiological pathways as altitude-camps: Make your body live with reduced oxygen for a while, so it adapts by making more blood cells – then remove the restriction (be it altitude, or CO) and you should have a performance benefit.
The altitude camps cost thousands and thousands – flights, hotels – and have social costs (time away from family). The CO method is cheap and can be done anywhere.
If you ban CO rebreathing then all you do is help the teams at the very top who can afford the altitude camps (plus the highest hotels in Europe are already booked out by the big teams for the critical periods in the season, for years to come).
What a dumb dumb controversy.