The best summary of the passage-Cheating in marathons:
The organizers of Marathons have started adopting various ways and means to identify and track cheating in races. They are using a combination of humans and technology to do so. From a lightweight computerized chip attached to the participant’s shoe keeping track of his time at different points, installing secret video cameras at secret locations on the course to employing volunteers staying scattered on the course, keeping an eye on the runners recording their number and time, they do it all.
Apart from that, irregular sweat patterns, lack of salt stains on a runner’s face and inappropriate clothing also help. Remembering the course and other runners on the way well are the precautions runners should take to save themselves.