AA3 has been rumoured to have very, very bad effects on your knees.
It may look like its helping at first, but 10 years down the line, who knows.
I was going to start AA2 and AA3, but when i was doing some of the excercises, I noticed a painful cracking in my knees, so I instantly stopped.
It was only a few months after that then I heard that it may cause problems with your knees, so a little light went off in my head that told me 'Ah, so I was right!'
My advice; don't dont Are Alert.
(Just incase you want to know, my knees are fine now, i found some very good light excersises that have reduced the cracking considerably. Funily enough, my knees only got to that state from doing too many big jumps, into landing or badly excecuted rolls, a lesson about rolling I learned the hard way.)