Fifteen of the 558 athletes in the U.S. delegation at the Rio Olympics – or slightly less than 3 percent – had therapeutic-use exemptions in force during the games.
The exemptions, known as TUEs, came under increased scrutiny last week after Russian hackers broke into the database of the World Anti-Doping Agency and posted confidential medical information online from some athletes.
TUEs let athletes use otherwise-banned substances to treat long-standing medical conditions, such as attention-deficit disorder and asthma. Proponents argue those exemptions only level the playing field; critics say they can give competitors an edge.
The hackers largely targeted U.S. female Olympians, among them tennis stars and sisters Serena and Venus Williams, and gold medal-winning gymnast Simone Biles. All three, as well as several other prominent athletes whose medical records were posted, said the data strongly supported their use of a TUE.
“I am one of the strongest supporters of maintaining the highest level of integrity in competitive sport and I have been highly disciplined in following the guidelines,” Venus Williams said in a statement.