Re: Start martial arts fight?

@Sunny_Rio  Your sim can Ask to Spar with another sim that has the skill.  Or at a certain level (maybe 4?), your sim can enter tournaments in China.  To do so, call the opponent on the phone; there should be an option to "invite over next ranked opponent" or similar, like you'd see with chess opponents.  In theory, this could work in the homeworld, but there probably aren't any other sims with the skill.

And no, you can't karate chop a random sim instead of fighting.  Having a higher Martial Arts skill will make your sim more likely to win a fight though.