For what it's worth, you can use your arm to support it if you're armored as well. If you're in chainmail/plate, the force is distributed well enough that ther

For what it's worth, you can use your arm to support it if you're armored as well. If you're in chainmail/plate, the force is distributed well enough that there's no reason you can't do this, even with a double-edged weapon. That said, there are many swordfighting styles where armor hinders you significantly, and you frequently see single-edged weapons in these. It's actually really interesting to study the history of swords, their techniques, and the armor commonly used along side them -- used to have a really good book about this, but can't find it now.