A good friend took a karate class years back (not Tanaka's).  After his first year he was to demonstrate to an audience how to break a board.  "Whap!" and the board broke in half.  After the demonstration was over, I walked over and grabbed one of the unbroken boards.  My friend held it. "Whap!" The board broke in half.  Looking the things over they were cedar planks cut against the grain.  Anyone with half a hand and a gimpy leg could have splintered one.  I highly doubt anyone could pulp a tree, including Tanaka. Makes for a good story though!