Be careful you make clear what physical aspect you are talking about. Pulling Gs is not the only thing to be concerned about. In fact it is often said that for pulling Gs you ought to be short, fat and have high blood pressure. The Air Force doesn't want two of those. I don't know exactly what they are doing for PT during training these days but the day of "fatties" doing fine is gone. A few years ago the Air Force started mandatory PT standards which consist of running, push-ups, sit-ups and a waist mesurement. Each of these except the waist measurement is based on sex and age. Running is the biggest factor but the waist measurement takes a lot of guys down. You don't want to be struggling with the physical standards at the same time you're dealing with the flight training. No it is nothing like Marine boot-camp. You will have to do some form of officer training before you can go to UPT anyway that will have a higher level of PT than pilot training. If you can't make the physical requirements there you won't have to worry about UPT. It's not tough in the big scheme of things assuming you can run but don't be complacent about it.