I posted this in my greeting thread too, but wish to ask the following. Doesn't all these methods rather make your shin bone to weaken? I know it is actually about the nerves, but can't see how beating up your shin bones are going to make it physically stronger. I can only see it causing your shins to get weaker. Is my logic flawed here?
You can certainly go overboard and fracture or break a bone in training but the shin is really tough. If you are kicking a bag -- which absorbs a large portion of the impact, you're about as safe as you can be. Repeatedly striking with any bone in your body will, over time, build up these rigid mineral tissues which actually reinforce the existing bone. It is one of your body's natural defences to bone injury.