The Union Cycliste Internationale (UCI) has officially banned the repeated inhalation of carbon monoxide (CO) in cycling, citing the potential health risks associated with its use. The ban, set to take effect on February 10, 2025, comes after the UCI’s Management Committee met in Arras, France, in late January.
Carbon monoxide rebreathing is used in sports medicine to measure haemoglobin mass and blood volume, this method is also used by WorldTeams to measure altitude training response.
Several teams were using the haemoglobin mass measurement method to optimise altitude training, as revealed by Escape Collective at last year’s Tour de France. Visma-Lease a Bike, UAE Team Emirates, and Israel-Premier Tech confirmed they utilised this method to quickly and accurately monitor key blood values, and better track the physiological response of its athletes to altitude training by having riders inhale small amounts of CO.
However, as also reported by Escape Collective, a growing body of recent scientific research suggests that higher and more frequent doses of CO could significantly impact key measures of aerobic capacity, such as Vo2 max (maximal oxygen uptake).
Carbon monoxide is a poisonous gas and can cause serious health issues, including headaches, dizziness, nausea, and even more severe risks, such as heart complications, seizures and death.
The UCI’s new regulation restricts the use of CO re-breathing systems, prohibiting possession of these systems outside medical facilities (albeit without offering an exact definition of ‘medical facilities’) and placing an outright ban on CO inhalation for performance enhancement. A statement published by the UCI today reads, “this ban applies to all licence-holders, teams and/or bodies subject to the UCI Regulations and to anyone else who might possess such equipment on behalf of riders or teams.”
Under the new guidelines, CO inhalation will still be allowed within medical facilities, but only once per athlete to assess haemoglobin mass. Any subsequent CO inhalation must occur two weeks after the first measurement. For top-tier teams, such as UCI WorldTeams, Women’s WorldTeams, and ProTeams, any use of CO for this purpose must be documented in the athlete’s medical file, in compliance with UCI’s medical regulations. The UCI has also urged the World Anti-Doping Agency (WADA) to take a stance on this practice.
The UCI first announced its plans to ban the repeated use of CO in December. That ban is now confirmed and President David Lappartient said the World Governing Body’s “priority is to protect the health and safety of our athletes, and today’s decision is another significant step in this direction.”
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