""RAIN & MUD CONDITION"" EE WAS RETURNING A TROUGHING ROLLER SET TO THE BACK OF THE MAINTENANCE TRUCK. HE THEN BACKED AWAY FROM THE TRUCK AND SLIPPED IN THE MUD. WHEN HE STARTED TO SLIP, HE TRIED TO CATCH HIS BALANCE. HE THEN FELT AND HEARD HIS BACK POP AND INSTANTLY HAD LOWER BACK PAIN.