28 November 2013 Last updated at 12:41

Michael Phelps could 'no doubt' win medal at Rio Olympics - Bowman

Bob Bowman, the man who coached Michael Phelps to 18 Olympic gold medals, tells BBC Sport's Nick Hope that if the swimmer does return he could challenge for honours at the 2016 Rio Games.

The 28-year-old has resumed training and rejoined the drug testing programme in May 2013 to leave open the possibility of a racing comeback.

Phelps retired after winning his 22nd Olympic medal at the 2012 Olympics in London, but could be eligible once again come March 2014.