EMPLOYEE FELT A SMALL TWINGE IN HIS LEFT LOWER BACK WHEN PICKING UP A SMALL BARRELL OF GREASE THAT HAD TIPPED OVER WHILE HE WAS CHANGING A DISPENSER. ABOUT 15 MIN. LATER, HE PICKED UP A 5 GAL LON BUCKET TO EMPTY THE WATER OUT. HE WAS UNABLE TO PICK UP THE BUCKET AND FELT SEVERE PAIN IN HIS LEFT LOWER BACK.