EE WAS LIFTING MANCAGE DOOR-THE DOOR HAD BEEN HARD TO OPEN BECAUSE OF ITS WEIGHT. WHEN ATTEMPTED TO OPEN THE DOOR HE TWISTED HIS BACK. HE HAD PULLED A MUSCLE IN HIS BACK 2 MONTHS PREVIOUS LIFT ING THE SAME DOOR. HE AGGRAVATED AN OLD INJ. ALTHOUGH THE ACCIDENT HAPPENED ON 4/30/03, EE WENT BACK TO HIS NORMAL JOB UNTIL 5/22/03.