In our instruction class, we teach the technique, you partner up with someone, you very slowly run through the technique with that person as a drill, it’s a muscle memory drill.  After the end of that class for those that want to they can stay for the second class, which is a sparring class.  Probably half the people stay for that.  Yes just like any other activity you are bound to get an injury.  I have probably been hurt more than most because I am on the mat every day.  In our history and philosophy we follow the 753 code, in that code it is a guide on how to live, physically and mentally, and one of the things I like to focus on is being positive.  I don’t celebrate getting hurt, but I do look at it and say how can this injury help me, how can this injury teach me to use other parts of my body, or how can this injury get me to look at self defense differently.  Because in reality if you get hurt you can’t tell your attacker, hey wait I’m injured.  So anytime I get an injury I do whatever I have to do to train around it.  In our advanced classes we will do handicapped training on purpose, like one handed training just to teach how to work around it.