Carbon monoxide and other “tricks” in sports: does the winner take it all?

1. Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland

In the relentless pursuit of success and fame, many athletes and teams are willing to exhaust nearly all possible means to gain a competitive edge, which was seen also during the 2026 Milano-Cortina Winter Olympics. While this may include even doping, it more commonly involves exploiting technological innovations and advanced training techniques (1–4), which have likely contributed—at least in part—to the consistent progression of world records over the past century (5). One such approach, particularly in endurance sports but also gaining traction in team sports, is altitude training. Despite its popularity, its efficacy remains contested (6). Nevertheless, hypoxic chambers and other means to artificially stimulate hypoxic conditions are now allowed in most nations (7). Few months before the Olympics global media headlines wrote (8–13) that a Norwegian biathlon athlete was found dead in his hotel room during the altitude preparation training camp, with a hypoxia mask on his face. This tragedy illustrates that some athletes may be willing to adopt increasingly demanding methods in pursuit of performance gains.

Within this highly competitive culture, athletes may feel compelled to adopt any method perceived to provide an advantage, regardless of whether robust scientific evidence supports its effectiveness and safety. A recent controversial method drawing attention to athletes is the repeated inhalation of carbon monoxide (CO), with some studies suggesting a potential increase in hemoglobin mass and exercise performance (14–17).