London Olympics | Track and field

Carmelita Jeter carries the American flag after winning the silver medal in the 100 meters at the 2012 London Olympics.  (Wally Skalij / Los Angeles Times)

Jamaica’s Shelly-Ann Fraser-Pryce, left, defeats Carmelita Jeter of the U.S., right, and Nigeria’s Blessing Okagbare to win the 100-meter gold. Jeter won the silver.  (Wally Skalij / Los Angeles Times)

American sprinters, from left, Tianna Madison, Carmelita Jeter and Allyson Felix watch the replay after the 100m race. Jeter was the only one to place, taking home a silver medal.  (Wally Skalij / Los Angeles Times)

Britain’s Mo Farah, left, wins gold ahead of the United States’ Galen Rupp in the men’s 10,000-meter final.  (Kirsty Wigglesworth / Associated Press)

Great Britain’s Mohamed Farah, left, celebrates his victory in the 10,000-meter race with second-place finisher Galen Rupp of the United States.  (Wally Skalij / Los Angeles Times)

Galen Rupp of the United States smiles after winning the silver medal in the 10,000-meter race at the London Olympics.   (Wally Skalij / Los Angeles Times)

Gold medalist Chen Ding of China walks in the final lap of the men’s 20-kilometer race walk near Buckingham Palace.  (Charlie Riedel / Associated Press)

Great Britain’s Jessica Ennis celebrates the gold medal in the heptathlon after winning the 800m race, the final event.   (Wally Skalij / Los Angeles Times)

Jessica Ennis of Great Britain celebrates winning gold in the women’s heptathlon.  (Ian Walton / Getty Images)

Estonia’s Grit Sadeiko pauses on the track after the final leg of the heptathlon, the 800 meters. Jessica Ennis of Australia won the gold medal in theheptathlon  (Wally Skalij / Los Angeles Times)

United States’ Will Claye won a bronze medal in the men’s long jump. Greg Rutherford of Great Britain won the gold medal.   (Matt Dunham / Associated Press)

Jamaica’s Usain Bolt, left, wins his qualifying heat of the 100- meter race.  (Wally Skalij / Los Angeles Times)

Ryan Bailey of the United States, left, wins his 100m heat.  (John G. Mabanglo / EPA)

Tyson Gay of the United States qualifies for next round of 100m race.  (Adrian Dennis / AFP / Getty Images)

Justin Gatlin of the United States salutes after qualifying in his heat of the men’s 100-meter race.  (Lee Jin-man / Associated Press)

United States’ LaShawn Merritt, the defending Olympic champion in the 400-meter race, walks off the track after injuring his hamstring during the first round of the 400m race in London.  (Wally Skalij / Los Angeles Times)

Oscar Pistorius sprints toward the finish line in the first round of the 400 meters. The double amputee from South Africa finished second in his heat to qualify for the semifinals.  (Wally Skalij / Los Angeles Times)

South Africa’s Oscar Pistorius, running on carbon-fiber prosthetics, qualified for the next round in the 400-meter race.   (Wally Skalij / Los Angeles Times)

Croatia’s Sandra Perkovic celebrates after winning the women’s discus throw.  (Adrian Dennis / AFP / Getty Images)