Never even heard of this. Guess it makes a kind of sense though- isn't that how muscles grow? Slightly over-training/stetching them causes small rips- which become stronger (and beefier I guess) when the body repairs them. Guess bones work in a similar way.
Imagine it could go very wrong but I guess if you know how hard to hit and where. What do you hit yourself with? Don't feel obliged to answer- I'm just curious really.