Exclusive: Tour riders are inhaling carbon monoxide in ‘super altitude’ recipe

Multiple Tour de France teams are using carbon monoxide rebreathing devices for altitude training, a controversial practice that can be potentially dangerous. The technique involves inhaling a controlled mixture of oxygen and carbon monoxide to stimulate the production of erythropoietin, which increases red blood cell count and hemoglobin mass, thereby enhancing oxygen transport. While the method is not illegal, it raises concerns due to the risks associated with inhaling carbon monoxide, a potentially deadly poison gas. The World Anti-Doping Agency has not commented on the practice, and researchers have not yet determined the actual performance gains or optimal dosage for athletes.

Tour de France teams have been using carbon monoxide inhalation to optimize their athletes' altitude training. At least three teams, including Visma-Lease a Bike and UAE Team Emirates, have access to a carbon monoxide rebreather, which allows for the precise dosing of carbon monoxide into the lungs. While the technique is not banned by the World Anti-Doping Agency (WADA), it appears to conflict with the agency's rules around artificial manipulation of the blood. Carbon monoxide inhalation can have a powerful impact on measures of aerobic capacity like VO2max, or maximal oxygen uptake, and can be used to prolong or even replace the performance-enhancing benefits of altitude training.