Cycling's governing body has banned the repeated use of carbon monoxide rebreathing that some riders misuse to artificially increase their performances.
Following a meeting of its executive committee Saturday in France, the UCI said it approved a ban on repeated inhalation to protect the health of riders. The ban starts Feb. 10.
The inhalation will, however, continue to be authorized "within a medical facility and under the responsibility of a medical professional experienced in the handling of this gas for medical reasons," the UCI said.
The use of carbon monoxide was put in the spotlight during the Tour de France when the cycling website Escape Collective reported that riders from multiple teams inhaled the toxic gas to optimize altitude training.
The gas can be used as a tracer to monitor the diffusion of oxygen in the lungs or the total mass of hemoglobin, a key blood value for racers. Two-time Tour de France champion Jonas Vingegaard said last month that some are using the method to dope "by regularly inhaling low doses of carbon monoxide, which leads to a significant increase in the performance."
The UCI decided to act on medical grounds, saying the gas, when inhaled repeatedly in non-medical conditions, "can result in acute and chronic health problems, for example headaches, lethargy, nausea, dizziness, and confusion."
"Such symptoms can worsen at any time and develop into problems with heart rhythm, seizures, paralysis, and loss of consciousness," it added.
The new rules prohibit the possession, outside of a medical facility, of commercially available CO rebreathing systems connected to oxygen and CO cylinders, the UCI said.
When performed under medical supervision, the UCI said only one inhalation will be authorized to measure the total mass of hemoglobin, with a second inhalation allowed only two weeks after the first measurement.
The method remains authorized by the World Anti-Doping Agency. The UCI said it has requested the body to take a position on the issue.