Acrobatic Flying

A couple of days, I watched the Red Bull Air Race final in Perth and I wonder who are these drivers. Are all military pilots or are they the drivers online?
Is it enough to have the medical class 1 for aerobatics? ... Or is it a special medical examination for them?
Oh I am so ignorant, yeah, but I "never felt this before.
Thank you in advance

The only thing you need is a private pilot license and a type rating for the aircraft you want to fly in. Then, it is advisory to take some lessons from a pro. Cascades push the plane to the edges of its performance to better understand something about aerodynamics and aircraft performance (these things are part of your theory of flight training, then I suggest attention). You'll deal with G-Nice forces to choose a plane that can lift the load factors of strokes.

One last thing! do not practice the urban area of more ... citizens can get some ribs and call the police ...

No, they do not need military pilot, I took some lessons in aerobatics and it was a pleasure!

Well, here in Canada, all you technically need a private pilot license and an aerobatic aircraft that can do if you do not intend to carry all passengers. It is strongly recommended that you get training before you embark on your own.

does not fly very well

Not if you buy an aerobatic aircraft as an extra and get a license to use, what's stopping you?