EMPLOYEEAND CO-WORKER WERE CARRYING AIR CONDITIONER UP STAIRS. EMPLOYEE WAS WALKING BACKWARDS UP STAIRS. THEY STOPPED AND CO-WORKER LET WATER DRAIN OUT OF AIR CONDITIONER. THIS PUT A STRAIN ON EMPLOYEE'S BACK. HE DID NOT REQUEST TO SEE COMPANY DOCTOR UNTIL 03-15-2000. THIS REPORTABLE AS HE WAS PUT ON A WEIGHT LIFTING RESTRICTION OF 20# FOR TWO WEEKS.