"We have never used it to enhance performance" — INEOS forced to admit CO usage as report claims riders had to sign consent forms during 2025 training camp

INEOS Grenadiers have confirmed the use of carbon monoxide (CO) rebreathers during a 2025 training camp, following a report by The Times that claimed riders had been asked to sign consent forms before undergoing the now-controversial testing method.

The British team had initially denied employing CO rebreathers in 2024, including during the Tour de France, after allegations surfaced linking several WorldTour outfits — including UAE Team Emirates, Team Visma | Lease a Bike and Israel-Premier Tech — to the use of the performance-monitoring technology. However, documents obtained by The Times show that INEOS did conduct carbon monoxide rebreathing tests in Room 101 of the Syncrosfera Fitness and Health Hotel in eastern Spain, just days before new anti-doping rules came into effect.

The Times wrote in their report: “It was only when confronted with The Times’s knowledge of the testing in Spain, and the fact that the team’s director of communications had denied conducting tests during the 2024 Tour de France, that INEOS confirmed their use of carbon monoxide.”

In a statement issued to Road.cc, the team maintained that its use of the method was strictly diagnostic: “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," INEOS continued. "We have never used it to enhance performance and have always adhered to UCI rules and regulations on this issue.”

The testing, according to The Times, involved seven riders — some reportedly teenagers — inhaling a mixture of oxygen and carbon monoxide for five to six minutes, followed by a short rest and then a second test. While experts cited in the report noted that repeated testing in one session can be standard scientific practice to establish an average value, the procedure's timing raised eyebrows.

The second round of tests took place on February 1 — the very same day the World Anti-Doping Agency (WADA) announced new measures restricting carbon monoxide rebreather use. From February 10, the UCI introduced a rule limiting CO inhalation to a single test per two-week period, with usage only permitted under strict medical supervision for diagnostic purposes.

The report also states that the tests were overseen by a professor from the Inland University in Lillehammer, Norway, who has since joined Q36.5, another UCI-registered team. Sources told The Times that not all participating riders had been involved in altitude training at the time, and one reportedly experienced nausea and breathing difficulties during the back-to-back sessions.

INEOS’ acknowledgement comes amid a wider reckoning in professional cycling over the ethics, legality and potential performance-enhancing effects of carbon monoxide rebreathing, a technique originally developed in the 1980s to measure total haemoglobin mass (Hb-mass). While long considered a valid diagnostic tool, concerns have emerged over whether repeated usage could stimulate erythropoiesis — the production of red blood cells — thus mimicking the physiological adaptations of altitude training.

WADA has now included non-diagnostic use of carbon monoxide inhalation on its 2026 Prohibited Methods list, citing evidence that the method can induce hypoxia and increase erythropoietin production under certain conditions. The UCI’s ban already covers repeated use, and mandates medical oversight for all diagnostic applications.