7 time Olympic Medalist Eero Mäntyranta had a gene mutation that allowed him to carry 50% more oxygen in his body.

Eero Mäntyranta was a Finnish skier and multiple Olympic Medalist . He competed in four Winter Olympics (1960–1972) winning seven medals at three of them, making him one of the most successful skiers Finland has ever produced. His success at the 1964 Winter Olympics earned him the nickname “Mister Seefeld”, referring to the venue where the cross-country skiing and biathlon competitions took place. The Finnish Ministry of Education endowed him with the Pro Urheilu letter of recognition in 2000. There is also a museum centered on Mäntyranta in his birthplace of Pello.

Mäntyranta was the first Finnish sportsman to test positive for doping. At the 1972 national championships, his tests showed use of amphetamines, but the result was hushed up. After the Sapporo Winter Olympics, the fact came to light but was denied by Mäntyranta. Later Mäntyranta admitted to using hormones, which during his sports career were not prohibited.

Mäntyranta had primary familial and congenital polycythemia (PFCP) causing an increase in red blood cell mass and hemoglobin due to a mutation in the erythropoietin receptor (EPOR) gene, which was identified following a DNA study done on over 200 members of his family, as reported in 1993. This condition results in an increase of up to 50% in the oxygen carrying capacity of the blood, a large advantage when participating in endurance events.