"That didn't prevent the 2016 Philadelphia Marathon organizers from placing an unannounced mat at a turnaround point 22 miles into the race. It helped them catc

"That didn't prevent the 2016 Philadelphia Marathon organizers from placing an unannounced mat at a turnaround point 22 miles into the race. It helped them catch hundreds of cheaters." That sounds like a nice and easy way to weed out a lot of cheaters - every race has one or two randomly placed timing mats.