What do 'doping whispers' say about anti-doping and the state of sport?

The 'whisper' that seems to follow every athlete that wins and especially those who break records, dominate their fields or see a dramatic improvement in performance…is he/she doping? The Olympics has once again seen some astonishing performances and world records broken. However, many of these exceptional performances have been questioned in the media and even by the winning athlete's competitors. Take for example, South African Wayde van Niekerk, who smashed Michael Johnson's 17-year-old 400-metre world record. One of the first questions he was asked upon winning was about how he would respond to people who said he was on drugs. Likewise, Ethiopia's Almaz Ayana faced accusations from her fellow competitors after breaking the world record in the women's 10,000 meters by more than 14 seconds. And, most recently, the success of the British cycling team has been questioned: how is it they are performing so well?