A 4-ship BFM sortie...split into pairs, "go to your corners and at the bell come out fighting..." you separate and then come at each other, reach the merge, break, and the fights on!
You run several of these over 30-45 minutes, run yourself out of gas (fuel and human energy), recover to the field, and go into a 2-3 hour debrief. I've lost 5-10 pounds of water weight in a fight like that from fighting the G forces. For folks my size (6'2, 225) it was weight training and repetition that allowed us to fly that way as a norm.
I haven't been in a fighter squadron that didn't have a decent little gym for weight training. And of course, the base gym would be loaded with folks.
Oh, and when speaking of the centrifuge...it was mentioned above...in the AF if you're going to fly fighters...you must pass this pig. And to pass, unless they've changed the standards, you will have to successfully "fly" a 9G turn for 15 seconds. And that is NOT FUN. Put simply: IT HURTS.
If you PASS, you're all smiles...if you don't, you get recorded doing the funky chicken...