Ineos Grenadiers admit to using now-banned carbon monoxide rebreathing test – but team insist they did nothing wrong

Ineos Grenadiers have admitted to the use of carbon monoxide rebreathers, the controversial method now banned for non-diagnostic purposes by WADA and used by other teams, such as Visma-Lease a Bike and UAE Team Emirates, purportedly as a means of testing and optimising riders’ altitude training.

While Ineos denied that they had used the dangerous rebreathers – which have also been linked to performance enhancement – for testing purposes at the 2024 Tour de France, the British squad have since confirmed that they were later utilised in early 2025 as a “measurement method” at a training camp.

An itinerary seen by The Times shows the tests were carried out days before WADA introduced measures to restrict their use, while Ineos have stressed that carbon monoxide was never used to “enhance performance” and that the British squad “always adhered to UCI rules and regulations on this issue”. 

According to the document viewed by The Times, CO rebreather tests were conducted in Room 101 of the Syncrosfera Fitness and Health Hotel in eastern Spain during an Ineos training camp earlier this year. 

> What is carbon monoxide rebreathing and why is the entire Tour de France talking about it? Tadej Pogačar and Jonas Vingegaard insist it’s “nothing suspicious” and “just a simple test”, but others are less convinced

The itinerary reveals that seven cyclists had taken the test over two days, some of whom were teenagers. They were asked to sit on a bed and inhale a mixture of oxygen and carbon monoxide for five to six minutes. They had a break of around 15 to 20 minutes before doing it again. 

Several experts have said that it would not be unusual to conduct two tests, a few minutes apart, as they can get a more reliable, average measurement. 

The second day of the use of carbon monoxide rebreathers was February 1, the same day that WADA announced that its use would be banned.

The new rules stated that from February 10, only “one CO inhalation to measure total Hb mass will be permitted. A second CO inhalation will only be authorised two weeks after the initial Hb measurement.” 

The riders had to sign consent forms before undergoing the tests, which were overseen by a professor at the Inland University in Lillehammer, Norway, who is now working exclusively for Q36.5. 

Two sources said some of the riders called were not involved in altitude training at the time. They said at least one felt nauseous and struggled to breathe by the end of the back-to-back tests.

The controversy surrounding carbon monoxide rebreathers followed 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.

Ineos Grenadiers denied the use of the test. However, after being confronted by The Times with knowledge of the testing in Spain, Ineos confirmed its use of carbon monoxide following the 2024 season. 

Ineos told road.cc: “This is a measurement method developed during the 1980s and used widely ever since. As publicly known, teams in the peloton and across other sports have been measuring HbMass through this method for several years.

“The INEOS Grenadiers did not use this method in the 2024 racing season or seasons before that – for the avoidance of doubt, that includes the 2024 Tour de France. 

“The team has since used this as a diagnostic tool – this has only ever been used as a measurement method to check how individual riders respond to altitude (this can be simulated or natural altitude) as well as heat stress and training. 

“We have never used it to enhance performance and have always adhered to UCI rules and regulations on this issue.” 

When questioned following the controversial report, UAE Team Emirates, Visma-Lease a Bike and Premier Tech confirmed that they had access to the equipment for testing, but any alternative use has not been proven. 

“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.”

Tadej Pogačar also said:  “It’s a test in altitude camp to see how you respond to altitude. You need to do this test, it’s like a two or three-minute-long test. You breathe into a balloon for one minute, and then you see the haemoglobin mass, and then you need to repeat it two weeks after.

“But I did just the first part of the test. I never did the second part because the girl who was supposed to come after two weeks didn’t come. It’s not like we’re breathing exhaust pipes every day in the cars. It’s just a pretty simple test to see how you respond to altitude training

A UAE Team Emirates spokesperson added, “It is a well-established, safe, professional method that is backed by a very large amount of research. It is used widely by athletes, climbers and other persons who are exposed to altitude for professional sports or other physical activities.”

“It’s not a therapy; it’s a diagnostic tool that we use to essentially work out what our athletes’ physiology is,” the team’s medical director Adriano Rotunno told Escape Collective. 

Israel Premier Tech also said, “sole use of the Detalo Blood Volume Analyzer is for testing purposes to measure the impact of altitude training”.

However, retired French rider Romain Bardet did suggest that it could explain the jump in form from some riders. 

“We see the studies. Anything is possible. I have never heard of anything, but at the same time, I would not be surprised,” said former DSM-Firmenich PostNL climber Bardet. 

“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.

“Carbon monoxide could explain the trajectory of some people we didn’t know about a year, a year and a half ago, but it’s also a bit of an easy claim to make without looking at their trajectory.

The non-diagnostic use of the gas is now banned, as it can increase erythropoiesis under certain conditions,” according to the WADA. 

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.