THE EMPLOYEE WAS PREPARING TO POSITION A PALLET IN ORDER TO STACK 100 LB BAGS OF SAND WHEN THE ACCIDENT OCCURRED. HE HAD PICKED UP A WOODEN PALLET FROM A STACK OF 3 PALLETS ON A CONCRETE FLOOR AND SLID IT VERTICALLY ACROSS THE FLOOR 6', THENLOWERED ONE SIDE TO THE FLOOR WHEN HE FELT A SHARP PAIN IN HIS LOWER BACK.