Nightmare Fuel: How the contestants are surgically prepped for the game. The legs from groin-level down are cut off, with or without anesthesia, then their skin is stripped off in a method similar to sandblasting. Next, a sheet of malleable metal is grafted onto in place of the skin, especially since the arms are how they move around. Afterwards, vacuum-esque suckers are attached to their hands, to allow them to climb walls and pick up items. Presumably the cannons are attached where the legs would be. Barring the final sentence, that was paraphrased from the manual.