The updated measures for the Columbus Marathon also ban non-athletes from the course and prohibit anyone but registered runners or walkers from crossing the finish line.
Organizers of Sunday's race warn that even people carrying a child in their arms as they cross the line risk disqualification.
Races around the country have beefed up security following the April Boston Marathon bombings that killed three and injured hundreds.
Columbus is also banning large bags or backpacks carried by spectators who plan to sit in bleachers at the start.
Eighteen thousand people are expected to run in the marathon and half-marathon.