THE EMPLOYEE WAS SITTING IN THE DRYER CONTROL ROOM. AS THE EE ATTEMPTED TO STAND UP, HE COULD NOT STAND UP STRAIGHT. THE EE FELT A LOT OF PAIN IN HIS LOWER BACK & WAIST AREA. 30 MINUTES PRIOR TO THIS ACCIDENT, THE EE HAD USED A METAL BAR TO BUST FROZEN SAND LUMPS STUCK IN THE SOUTH FEEDER (5-10 TIMES) & THEN SHOVELED SAND FROM UNDER THE TAIL PULLEY OF BC-17.