The UCI has announced its intention to ban the use of carbon monoxide (CO) by riders on medical grounds.
Cycling’s governing body will officially make its decision at the end of January on whether to ban the potential performance enhancing method of CO inhalation, while the haemoglobin mass measurement method will remain permitted.
“When inhaled repeatedly in non-medical conditions, [CO] can cause side effects such as headaches, fatigue, nausea, vomiting, chest pain, breathing difficulties, and even loss of consciousness,” the UCI’s statement read, explaining its position.
“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.”
This proposed ban comes after the UCI asked teams and riders publicly not to use repeated CO inhalation at its recent WorldTour seminar, and also requested the World Anti-Doping Agency (WADA) to take a position on the issue.
The UCI’s move to ban CO inhalation for potential performance enhancement on medical grounds mirrors its 2019 ban of the painkiller Tramadol, which was later added to WADA’s prohibited list in 2024.
Escape Collective revealed multiple teams at this year’s Tour de France were using the haemoglobin mass measurement method to optimise altitude training. Visma-Lease a Bike, UAE Team Emirates and Israel-Premier Tech all said they used this measurement tool to help them quickly and accurately track key blood values and optimise the powerful physiological benefits of altitude training for their riders by inhaling a small amount of CO.
However, a growing body of recent scientific research hypothesises an increased dosage of CO can have a powerful impact on measures of aerobic capacity like VO2max, or maximal oxygen uptake. This is what the UCI is moving to ban. There is no evidence any team including those named above are utilising this method.
Earlier this week at UAE Team Emirates’ pre-season training camp, performance coordinator Jeroen Swart told the media his team would no longer utilise the haemoglobin mass measurement method following an 18-month experiment with the technique.
“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,” Swart said.
“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.”
Swart went on to criticise Escape Collective’s reporting of CO inhalation, saying: “But 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. It doesn’t come across as realistic. So, I think there’s a lot of sensation.”
The UCI is yet to provide details as to how it will police its ban on CO inhalation, whether there will be permissible limits of CO that riders using the haemoglobin mass measurement method will have to stay below. What is key is that the protocol that leads to using CO for performance enhancement is now likely to be banned.
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