Hello, because I have not found any tutorial that allows me to automatically animate the bones with inertia (with the very tools of Blender) I decided to make a tutorial with a system that I have half-invented.
Here you have it, although it is described in Spanish I think it is understood anyway.
The starting point of this tutorial is this other tutorial from Blenderlounge
http://blenderlounge.fr/forum/viewtopic.php?f=21&t=1251