Science always brings us new facts that challenge us and challenge our perceptions of the world. For example, over the past five years, we have begun to see research into a type of compound, produced by the body, that is probably responsible for what we know as the ‘runner’s high’. Most of us know that the ‘runner’s high’ is the euphoric feeling that occurs when you run, but it also occurs when you do any task that is physiologically difficult. Linked with the runner’s high are a wide a...