Is astronaut training difficult?

You meet the same tests everyone else does. There is a bottom line every single day. It is not just periodic physical exams and running on treadmills. You get into an airplane and fly with people who trust their lives to your ability to fly. If you are not flying right, the community knows about it in one huge hurry, like now! If you are unable to do the job in an EVA suit, you find out every minute. Spaceflight does not require you to be an Olympian. The reason to be fit is to work 16 hours a day, decade after decade, to still hang in there. Then when you need to kick in a little more, it is there. It gives you some margin working in the space suit, although you should not need it. You want to design tools and the work so that it does not take muscle. If I am using muscle in a suit I stop in my tracks and say: "What are you doing wrong"? General spaceflight does not require superfitness