U.S. first lady Michelle Obama (C) jumps with four hundred children at an event on the South Lawn of the White House in Washington October 11, 2011, to launch a challenge to help break the Guinness World Records title for the most people doing jumping jacks in a 24-hour period. To break the record, more than 20,000 people from around the world must perform jumping jacks for one minute. REUTERS/Yuri Gripas (UNITED STATES – Tags: POLITICS SOCIETY TPX IMAGES OF THE DAY)