THE EE WAS SITTING IN DUMP TRUCK BEING LOADED WITH SAND/GRAVEL. THE LOADER OPERATOR DROPPED THE MATERIAL INTO THE DUMP BOX TOO HARD, WHICH CAUSED THE EE'S BACK TO POP AND LOSE SOME FEELING IN HIS LEFT LEG FOR A LITTLE WHILE. EE WENT TO THE DOCTOR ON 6/3/04. HE RECEIVED MEDICATION TO RELAX HIS BACK; NO RESTRICTIONS, RETURN TO DRIVE DUMP TRUCK.