In addition to the comment posted by the iaido-ka, those studying kobudo often don't start training with bladed weapons until 1st dan. Kamas are an excellent example (the little scythe-like weapon). When the student is ready they're given a set of wooden ones, and here's one of the reasons: When perferming or practicing a few of the techniques, the blade ends up on the opposite side of your back. If you're not careful, you end up removing your own kidney.
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