The team reportedly started using carbon monoxide rebreathing this season, with a frequency and setting that would now be restricted.
Ineos Grenadiers introduced the controversial carbon monoxide rebreathing technique to the team’s training repertoire this year, days before new UCI rules came into effect and in a way that now contravenes them, according to a Sunday Times report.
The team reportedly began using carbon monoxide (CO) rebreathing – they say for the first time – at a February 2025 training camp in Spain, at a frequency and in an environment that were strongly advised against by cycling’s governing body at the time, and are now forbidden under UCI medical regulations. The team’s tests were conducted in a 10-day window between the rules being published and a ban coming into effect, but came months after the UCI issued non-enforceable guidelines around the practice.
Ineos Grenadiers maintains that it has “always adhered to UCI rules and regulations on this issue.”
A bit of backstory
The use of carbon monoxide rebreathing in cycling first came to light at the 2024 Tour de France, when Escape Collective’s Ronan Mc Laughlin revealed that Visma-Lease a Bike, UAE Team Emirates, and Israel-Premier Tech were using the then-unregulated technique for testing purposes.
Exclusive: Tour riders are inhaling carbon monoxide to optimise altitude training
Top teams Visma and UAE confirm they have access to specialized equipment for testing, but deny using the potentially powerful new method for performance enhancement.
The technique was first established in the 1980s, allowing for precise dosing of carbon monoxide into the lungs. It is used in medical and scientific research settings – and now sport, too – to track key blood values. In a cycling context, it can be used to optimise heat and altitude training. The obvious downside is that carbon monoxide is potentially lethal.
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