Amber and Ryan are testing electricity. They want to test many different things like getting shocked with a Van de Graaff generator, getting a taste of electricity, and to push the limits they challenge 1 million volts.
Ryan and Amber are testing fear. They want to know how scared a person could possibly get before its too much. They also test some of their own phobias to see what there willing to do before it becomes overwhelming.
Ryan in the first season and second season tested less than lethal weapons used by armed forces on a daily basis, now he's at it again testing the latest advances in crowd control and person stopping devices.