United States' Dana Vollmer, left, reacts after winning gold and setting a new world record alongside Denmark's Jeanette Ottesen Gray following the women's 100-meter butterfly swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Sunday, July 29, 2012. Vollmer set a new world record with a time of 55.98. (AP Photo/Michael Sohn)

Photo by: Michael Sohn

United States' Dana Vollmer, left, reacts after winning gold and setting a new world record alongside Denmark's Jeanette Ottesen Gray following the women's 100-meter butterfly swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Sunday, July 29, 2012. Vollmer set a new world record with a time of 55.98. (AP Photo/Michael Sohn)