how to stop spline ik bones from going out the body ?

I finished this tutorial on how to make a jiggle bones but there are a problem in this tutorial spline ik bones go out the body you can see it in this minute 1:47 so how to fix it and stopping the bone from going out there

tutorial video https://www.youtube.com/watch?v=LHXJ2B0KqHs

Out where?