London Olympics | Track and field

Team USA women’s 4x100-meter team celebrate their world record run and gold medal victory.  (Morry Gash / Associated Press)

Carmelita Jeter of the United States takes the baton from Bianca Knight on the last leg of the 4x100 relay race.   (Wally Skalij / Los Angeles Times)

Keisha Baker of the United States, right, collides with Brazil’s Jailma de Lima during the 4x400 preliminary.  (Wally Skalij / Los Angeles Times)

Joshua Mance of the United States starts the second leg of the 4x400 relay.   (Wally Skalij / Los Angeles Times)

Jeffery Demps of the United States prepares for the start of a 4x100 relay preliminary heat.  (Wally Skalij / Los Angeles Times)

Kenya’s Hellen Onsando Obiri leaps over a fallen Morgan Uceny of the United States during the women’s 1500-meter final.  (Daniel Ochoa De Olza / Associated Press)

United States’ Morgan Uceny remains on the track after falling down as the winner, Turkey’s Asli Cakir Alptekin, crosses the finish line of the women’s 1500-meter race.  (Lee Jin-man / Associated Press)

An emotional Morgam Unceny of the United States leaves the track after falling on the last lap in the 1,500-meter race. She did not finish.   (Wally Skalij / Los Angeles Times)

Ethiopia’s Meseret Defar reacts as she crosses the finish line to win gold in the 5000-meter race.  (Lee Jin-man / Associated Press)

Ethiopia’s Meseret Defar puts a picture of the Virgin Mary on her face after winning the gold medal in the 5,000 meters race.  (Wally Skalij / Los Angeles Times)

Ethiopia’s Meseret Defar, left, embraces compatriot Tirunesh Dibaba after competing in a women’s 5000-meter heat. In the finals Defar went on to win the gold and Dibaba the bronze.  (Anja Niedringhaus / Associated Press)

France’s Renaud Lavillenie carries his country’s flag after winning gold in the men’s pole vault final.  (David J. Phillip / Associated Press)

France’s Renaud Lavillenie clears the bar in the men’s pole vault final on his way to a gold medal and an Olympic record.  (Hassan Ammar / Associated Press)

Tatyana Lysenko of Russia competes in the women’s hammer throw qualifications. She went on to win gold with an Olympic record toss.   (Bernd Thissen / EPA)

Poland’s Anita Wlodarczyk won the silver medal in the women’s hammer throw final.   (Pawel Kopczynski / Associated Press)

South Africa’s Oscar Pistorius running on prosthetic legs takes the baton from teammate L.J. van Zyl during the men’s 4x400-meter relay.  (Matt Slocum / Associated Press)