Back in 1969, naval researchers took blood samples from the crew of a Polaris nuclear submarine over the course of an eight-week patrol. Three-quarters of the sailors were smokers, so carbon monoxide levels were chronically elevated in the sealed confines of the sub. After a few weeks in this toxic miasma, the crew’s levels of hemoglobin, the crucial protein in red blood cells that ferries oxygen from the lungs to the muscles, had shot up by an average of 4.4 percent. Secondhand smoke had somehow turned the submariners into aerobic superstars.
This finding, along with others like it, was filed away for decades. After all, smoking destroys your lungs, so any performance benefits are outweighed by the harms. But then, last year, the idea exploded. Scientists published fresh data showing that huffing carbon monoxide could boost endurance. Other scientists responded with editorials warning against fooling around with a gas whose nickname is “the silent killer.” And headlines around the world trumpeted the news that Tour de France teams were inhaling the gas—confirmation, seemingly, of the cliché…
