Guten Tag!
What a good discussion topic!
Also: if you always hit your arms against a wooden dummy, for example, your bones will build out a thicker bone-skin
I've heard that constant shock to a bone, such as hitting a wooden dummy over and over, or jumping up and down (like a gymnast's feet) will cause the bone to become more dense. They say gymnasts have denser foot bones than regular people. So, I'm sure the same thing applies to striking a limb in martial arts.
They say iron palm training also makes the skin more dense.
But, I don't know that much about it so I'll let someone else take over.
IronFist
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