(Chicago, IL)  --  A woman from Portland is accused of cheating in the Chicago Marathon.  Twenty-eight-year-old Emily Clark finished the October 13th race with a time of 3 hours and 59 minutes-- under the average marathon finish time for a woman in the U.S.  A blog that investigates runners says Clark's pace changed suspiciously at the halfway point.  Clark was previously disqualified from the PeaceHealth Apple Tree Half Marathon in Vancouver for allegedly riding a bicycle for part of the race.  She has confessed to cheated in five previous races, including the Chicago Marathon in 2013.