The sex eligibility case of champion runner Caster Semenya has been one of the most contentious and most complex that sports has seen.

Bans on transgender women in swimming and rugby this week opened the door for track and field to consider following suit in what could turn into a wave of policy changes in Olympic sports.

Elaine Thompson-Herah of Jamaica won the 200-meter gold medal to complete her second straight Olympic sprint sweep.

The complex testosterone regulations in track and field have become an issue again at the Olympics after Namibian teenager Christine Mboma surprisingly won a silver medal in the 200 meters after being banned from running in the 400 because of her high natural hormone levels.

Thompson-Herah, seeking a second successive Olympics sprint double after bagging the 100m gold, matched her personal best from 2015 of 21.66 seconds.