EE WAS INVOLVED IN THE PROCESS OF REFILLING MULTIPLE TYPES OF OILS ON THE SERVICE TRUCK FROM 55 GAL. OIL DRUM LOCATED ON THE GROUND. THE DRUMS HAD TO BE MOVED IN ORDER TO BE CLOSE ENOUGH TO SERVICE TRUCK FOR TRANSFER OF OILS. THE MOVEMENT WAS BEING ACCOMPLISHED MANUALLY WHEN THE STRAIN TO EE'S LOWER BACK OCCURRED.