Even though he gave up his sword, Martin still felt he missed fighting. The thrill, the tension and the action of it especially. So, he thought of a non-violent alternative: wrestling! No one got hurt or killed, and it put his skills to good use. Eventually, after meeting many beasts from across the land, he found out about sumo.
So, to determine if one is a worthy fighter, Martin challenges them to a sumo match. An ultimate test of strength and skill, and both opponents are unharmed in the end.
Martin (c) Brian Jacques