INJURED AND CO-WORKER WERE CARRYING A PIECE OF PIPE, WHICH WAS ""L""-SHAPED, AND APPROXIMATELY 6"" X 48"" IN LENGTH (WEIGHING APPROXIMATELY 75 POUNDS), UP THE STAIR-WAY BETWEEN 6 AND 6 1/2 FLOOR IN PREP PLANT WHEN CO-WORKER'S END OF PIPE SLIPPED CAUSING INJURED TO FEEL PAIN IN HOW LOWER BACK.