At the starting line of a marathon, runners tend to worry more about the hills ahead and the training behind them than the possibility of a terrorist attack along the course.
But Monday's deadly explosions at the finish line of the Boston Marathon added safety to the list of pre-race worries for many athletes. With more than 26 sprawling miles to cover, is it even possible to keep major races secure?
All major marathons create protocols to deal with crises and enlist police officers to watch their courses, experts said. Given the nature of long-distance races that wind through urban centers and large crowds, though, there will always be some element of risk.
A marathon "has the classic elements sought by international or domestic terrorist groups or emotionally disturbed people," said Anthony C. Roman, CEO of Roman & Associates, a private investigation and security consulting firm. "They want to maximize the number of casualties and maximize media coverage."
Finish lines are especially vulnerable, Roman said, because they are packed with spectators, runners and members of the media. In an old colonial city like Boston, streets may also be narrow or otherwise hard to cover with security.
And while many sporting events bring together lots of people and TV cameras, marathons may be particularly exposed because there is no stadium entrance to be equipped with metal detectors. Marathons also cover so much ground that they pose many miles worth of challenges for police officers.
The best way to protect a marathon, Roman said, would be to begin long before the actual event with intelligence-based profiling that would identify areas of vulnerability. Before the race, all manhole covers along the route ideally would be sealed and garbage containers removed to minimize places where terrorists could plant bombs.
During the event, the course's sidelines and rooftops would be lined with uniformed and undercover officers who would look for suspicious activity. And bomb squads would do periodic sweeps of the course before, during and after the race.
Few events, however, have the money and manpower to be so thorough.