EE, IN A TWISTING MOTION, WAS THROWING STOCK MATERIALS TO AN UPPER LEVEL LOFT THAT IS 9 FT. OFF THE SURFACE. WHILE THROWING A CONTAINER THAT CONTAINED 6-1 GALLON BOTTLES OF WASHER FLUID WEIGHI NG 52 LBS. THE EE INJURED HIS LOWER BACK. BACK INJURY WAS NOT DIAGNOSED UNTIL OCTOBER 25, 2000.