Back problem

[Spanyard]

As I said in another posts, I'm a bboy who also is enthusiast of gymnast's conditioning, and I've been doing it since almost a year and a half.

Almost a year, I had a huge cramp in the back while breakin that I couldnt solve by only stretching, so I went to the physioterapist and she gave me some massages to improve, but my back didnt recover 100%. I had like 3 or 4 months were I had no problem, but when I started conditioning a lil bit harder, once again the pain came back.

Now I went to another physioterapist, and she told me that I have a little more curvature in my lower back than the normal ( I dont know how is it called in english), so she gave me some exercises to strenght some abs/hips muscles. I told her about back extensions and bridges to work the back and the lumbar muscles, and she said they were too agressive to the zone where my injury is, and she banned me from doing that.

So the question is about prepare the lower back and to work the back proplety, Im sure I did something wrong, mabye a postural thing, so I want to know if any exercise to work the back safety exists, and if not, some routines to work it safer.

Thanks a lot