Under 3 percent of US athletes in Rio had medical exemptions

Fifteen of the 558 athletes in the US 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.