DULUTH, Minn. — It may have been a self-professed fetish for slashing large rubber exercise balls that led a Duluth man to break into medical building Duluth in May. Christopher Neil Bjerkness, 31, pleaded guilty on Wednesday in St. Louis District Court to third-degree burglary. He was charged after someone broke into the SMDC-Duluth Clinic West building on May 30 and slashed the exercise balls there. The plea agreement calls for Bjerkness to spend a year at the Northeast Regional Corrections Center and participate in a sex offender treatment program. Bjerkness told Duluth police he slashed the rubber balls to satisfy a sexual urge. He tells the Duluth News Tribune that he can’t explain his fetish but says he suffers from other mental disorders.