EE WAS STANDING ON THE TRACKS OF A CAT 345 EXCAVATOR REPLACING A WINDSHIELD. HE TURNED TO ASK A FELLOW EE FOR A TOOL WHEN HE SLIPPED AND STARTED TO FALL. HE CAUGHT HIMSELF WITH HANDHOLD. TWIST ING AND PULLING HIS BACK. HE WAS TAKEN TO THE DR OFFICE AND DIAGNOSED WITH SPASM IN THE LEFT LUMBAR REGION AND BACK ON LIGHT DUTY UNTIL HEALER.