Other estimates suggest even higher numbers.A paper published in 2011 examined the prevalence of "blood doping", a catch-all term for ways to increase the capacity of blood to ferry oxygen to muscles.The researchers analysed samples from more than 2,700 athletes and concluded that 14% were probably guilty (though the tests fell short of explicit proof).That average concealed wide variations. Some countries had prevalence rates as high as 48%, though the researchers diplomatically refused to name the alleged offenders.Another study, published in 2018, simply asked more than 2,000 athletes whether they were doping.The data were collected in 2011 at two big competitions―the World Championships in Athletics and the Pan-Arab Games.To encourage honest responses, the researchers used what is called the randomised-response technique.This guarantees individual answers will remain anonymous and untraceable.They concluded that 43.6% of the athletes surveyed had doped in the past year.Translated to Tokyo, that would imply around 4,800 drug-boosted competitors―roughly in line with Mr Chalmers' fears.But all these estimates are just that: estimates."My gut feeling, from having worked with many Olympic-level athletes, is that the randomised-response numbers are too high," says Yorck Olaf Schumacher, who helped develop the Athlete Biological Passport (ABP),
