Th Russian record-holder has dominated the race for the past two years and a victory at the 34th annual race, which takes places on October 9, would put her in a class of her own as the only holder of three consecutive titles.

Counting Shobukhova, the Chicago Marathon has seen 12 back-to-back champions - seven women, including Britain's Marion Sutton, and five men.

To date, Kenyan athletes Catherine Ndereba and Evans Rutto are the only athletes to come close to scoring a hat-trick at the Marathon, after Ndereba won the 2000 and 2001 races, but was placed second in 2002, while Rutto claimed victories in 2003 and 2004, however dropped to fourth in 2005.

Khalid Khannouchi is the event's all-time leader with four victories over a span of six years, yet he was never able to string together more than two in a row, which he achieved in 1999 and 2000.

With its history of highly competitive elite fields, the inclusion of Shobukhova in the 2011 Chicago Marathon looks set to erase the statistic that sees it as the only event in the World Marathon Majors in which an athlete has never been able to beat all-corners for three consecutive years.

"I would like to thank the Bank of America Chicago Marathon for the opportunity to return to this world-class event for the third year in a row," said Shobukhova who was runner up in this year's Virgin London Marathon and improved her National record to 2 hours 20min 15sec in the spring.

"This year, there is additional pressure as I am the two-time defending champion and despite all the prior repeat champions, no one has yet been able to earn three straight victories in Chicago.

"Each year that I return I feel more popular there, the crowds recognise me, and I am more familiar with the course.

"This will help me run faster and possibly set another record, which is especially important in my preparation for the 2012 Olympic Games next summer."

A victory in the race would undoubtedly cement Shobukhova's status as a gold medal favourite for the London Olympics, with Chicago being her final marathon competition before the event in the English capital next year, as well as an invaluable opportunity to compete against a deep field of international competitors.

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