EMPLOYEE WAS CASE PACKING 14LB CARTONS INTO BOXES FOR SHIPMENT ON A TRIANGLE MACHINE. HE COMPLETED THE DAY'S WORK WITH NO PROBLEMS BUT WOKE UP EARLY THE NEXT MORNING WITH BACK PAIN. HE WAS SENT TO THE COMPANY DOCTOR & RESTRICTED FROM LIFTING GREATER THAN 20LB & GIVEN LIGHT DUTY. HE WAS RELEASED TO NORMAL DUTIES ON 4/11/00.