Having been through Cranwell recently, you'll find that they now place a large emphasis on self motivation blah blah blah. At the end of the day, this ethos extends because, in theory, you could be called to perform a task for the good of the country in any situation. I suppose fitness could be paramount. That doesn't mean you have to be able to run a marathon but you'd look a right tit in front of your men if you had to catch your breath walking up stairs. But then you could just be aircrew and get through the 'test' once a year......