I don't think you can turn them off, but you have some options...
You can destroy them or you can turn down their effectiveness.
I prefer turning down the effectiveness, and this is what they do in many special events.
Open your clipboard, and under arena settings go to the Weapons tab (I think; I'm at work and going by memory). Change the values for the top three items (GroundAutoLethality). Set them to the minimum and basically all you get is the effect and sound of them hitting you but do virtually no damage.