New gender testing guidelines for London Olympics

South Africa's Caster Semenya celebrates
South Africa's Caster Semenya celebrates taking silver in the women's 800 metres final at the International Association of Athletics Federations (IAAF) World Championships in Daegu on September 4, 2011.
MARK RALSTON/AFP/Getty Images

New International Olympic Committee guidelines will measure testosterone levels of athletes to determine if they qualify to compete as women.

Considered one of the most personal and controversial issues surrounding the Olympics, gender testing once again surfaced when South African 800m runner Caster Semenya blew past her competitors at the 2009 World Championships. Her gender was called into question and she underwent public scrutiny as she was investigated.

What is involved in this testing and why did one athlete so forcibly renew this controversy?