Scored a brown belt in MCMAP while enlisted, now I just spar on occasion with friends with martial arts/military backround to stay fresh. It works, plus the more you do it the less you physically feel pain, super duper useful. Just mind the occasional broken rib or two, maybe a clavicle sometimes but when it heals you have an awesome bone bulge that messes peoples knuckles up as they are twice as hard as the bone.