I once heard a (possibly apocryphal) anecdote about a record-breaking Nigerian sprinter. Somebody asked him how he managed to run so fast. His answer: "running is tiring and painful, so I like to get it over with quickly." The line is funny because it strikes us as fundamentally untrue. Great runners likely find running at least somewhat exhilarating and satisfying, otherwise they wouldn't do it without a lion chasing them. Running is not purely functional behavior. It is autotelic: an end in itself. Unlike purely functional behaviors, which cease when the external purpose is achieved (additional effort would be wasteful), autotelic behaviors persist indefinitely while they are enjoyable and sustainable.