EE WAS EXITING SIDE DOOR OF VAN ARRIVING AT MINE SITE PARKING LOT. HE STEPPED FROM SEAT, RIGHT FOOT ON GROUND, LEFT FOOT STILL IN VAN. AS HE WAS EXITING, FELT ""POP"" IN LOWER BACK WITH PAIN. HE REPORTED TO WORK, ATTEMPTED TO DRESS OUT, COULD NOT BEND OVER. HE SUSTAINED A LOW BACK SPRAIN.