In pre-Mongoose RQ, Martial Arts was a skill that doubled the damage of any unarmed attack (or other normally low-damage attacks that were appropriate to the style, e.g. shuriken for ninjutsu, bo stick for aikido, etc.) so long as the successful attacking roll was also under the Martial Arts skill. e.g. Unarmed 60%, Martial Arts 40%, any hit from 01-40 would do double damage, a hit roll from 41-60 would do normal damage. Like many Knowledge skills, the skill could only be raised by training or research, not by experience.