Race organizers were eager to invite them back — to let them finish what they started — and aware of the message that would send. If those people, like so many others, wanted to have some physical expression of resilience and determination, it would probably be that many of them at least would want to run the whole race, Boston Athletic Association executive director Tom Grilk said as he prepared for the 118th Boston Marathon. [...] there were the police and firefighters who helped at the site of the explosions; the doctors and nurses and volunteers and EMTs who tended to the wounded; the injured themselves, and friends and relatives who wanted to run in their honor or memory. The roads built in a horse and buggy era weren't made for tens of thousands of runners, nor the thousands of fans who cheer them on. "Anything that looked like a reaction that showed fear or in any way giving in to the acts of cowardly terrorists would have been very unfavorably received," he said. [...] instead of 18 men hitching rides to the start, a fleet of buses shuttles runners to Hopkinton. Security, which for a century remained in the background, became a bigger issue after the Sept.