ISTANBUL (AP) -- Reese Hoffa of the United States will seek a second gold medal in the shot put after winning at the 2006 world indoor championships.
The prelude for one of the big clashes at the London Olympics will be played out on opening day Friday when defending champion Jessica Ennis faces off against Tatyana Chernova in the pentathlon.
The two will compete in five events in one day, deciding who gets the bragging rights going into the Olympic heptathlon.
In the heats of the 3,000 meters, Ethiopian great Meseret Defar begins her quest to become the first female athlete to win five straight world indoor gold medals.
"This world championship is very special to me," Defar said. "I expect to win again."
Also competing for the U.S. is Sanya Richards-Ross, who has the best two 400 times of the year. Aleksandra Fedoriva of Russia may her closest challenger, along with the Russian team in the 4x400 race.
In the men's sprint, it will likely turn into another Jamaica-U.S. duel.
Lerone Clarke of Jamaica has been on a roll coming into Istanbul. He had the world's fastest 60-meter time until Trell Kimmons went to high altitude and ran 6.45 seconds in Albuquerque, N.M, knocking 0.02 off the mark.
Stars Olympic champion Usain Bolt and world champion Yohan Blake traditionally skip the indoor season.
Defar sees her race her as a vital preparation for the Olympics, where she will be trying to win back the gold medal she took at the 2004 Athens Games before finishing with bronze in Beijing four years later.
All eyes in Britain will be on Ennis. She won the 2009 world heptathlon title in Berlin and added the indoor pentathlon a year later, making her a pre-eminent home star for the London Games. A surging Chernova reached the pinnacle of the multi-event discipline last year in Daegu, South Korea, when she edged the Briton for gold in the outdoor seven-event heptathlon.
The world record has been at 4,991 points for 20 years and many feel the rivalry may be enough for one of the two to break the 5,000-point barrier.
"This is a dream for all sportsmen to break a world record," said Chernova, adding she's confident they would at least get close to the mark.
Another one who could get close is Sally Pearson, the hurdler who added a world title and election as woman athlete of the year in 2011.
The Australian won the national Olympic trials in 12.49 seconds on a wet and miserable weekend in Melbourne, the fastest time ever for a 100 hurdles on Australian soil. No woman has ever run a faster hurdles race this early in the year.
So, it is only logical she has a good shot at the four-year-old 60 hurdles world record of 7.68, held by Susanna Kallur of Sweden.
"My body is just ready to run fast," said Pearson, who rarely races indoors. "I have no idea what I am going to run out there."