REPAIRMAN WAS PERFORMING MAINTENANCE OF A PIECE OF EQUIPMENT. HE LIFTED A 120 LB. COMPONENT AND TURNED TO SET IT ON A HAND TRUCK. WHEN HE TWIST-ED, HE FELT A PAIN IN HIS BACK. HE CONTINUED WORKING AND RETURNED TO WORK THE NEXT DAY. HOWEVER, APPROX. TWO WEEKS LATER HIS BACK WAS HURTINGTOO MUCH TO WORK.