EE WAS USING A SLEDGE HAMMER TO BREAK UP ROCKS INT HE LONGWALL FACE CONVEYOR. AS HE WAS USING THE HAMMER HE FELT PAIN IN HIS LOWER BACK. FINISHED THE SHIFT BUT PAIN BECAME WORSE. THERE WAS NO DAMAGE OR IMPAIRMENT TO THE OPERATION OR TO ANY MINING EQUIPMENT. IMPROPER USE OF HAND TOOL CAUSED HE INJURY CONCRECTION NO OFTHER ALARM WERE INVOLVED.