James May discovers just how far he can push his body, exploring some of the most remarkable medical advances over the last hundred years. He begins by testing himself in a centrifuge, a machine used to train fighter pilots and astronauts. He is then invited to watch open heart surgery, where a man's heart stops beating in the middle of an operation. Fortunately, it is all part of the procedure to fit an artificial heart. But his biggest surprise comes when he investigates the 20th century's greatest medical breakthrough - the discovery of DNA. Show less