Okay, I have not yet tried this but it works for guns so a gel block should work for swords too. If you haven't seen demos on MythBusters or Fight Science, Ballistic Gel
can be molded into any form and a certain thickness block will accurately replicate muscle density. It has comparable density to animal meat, but none of the connective tissue, viscera, bone bits, and bloody mess. You can add other components to replicate bone structure too such as 1/2 inch bamboo.