At Saturday's Christie Clinic Illinois Marathon, 21 runners wearing shirts that read "Joe's Pacers" will stagger themselves throughout the area behind the starting line along with around 5,000 half-marathon and marathon runners and hold up signs affixed to long sticks.
Those runners are the official race pacers, and the time listed on that placard will be the time that athlete runs. Almost exactly.
"They are tasked with finishing the marathon within 30 seconds of the target assigned to them," said Jim Crist, director of the Illinois Marathon's official race pacers, marathonpacing.com. "That's 14,400 seconds, and I've got them doing something within 30 seconds, so that's within two-tenths of one percent accuracy.