all of the hardcore "martial arts" people in high school were legitimate dorks.
No one did MMA or boxing when I was growing up though. In later years I joined a real boxing gym where legit pros trained. Very meathead - but none were dorks.
nerds are always into power fantasies like superhero movies. martial arts is appealling because they can delude themselves into thinking they can hone skills irl that'll enable them to challenge stronger men. kip from napolean dynamite and dwight shrute are archetypes we've met irl. however notice that very few are into mma. the appeal is the fantasy of power, not their reality of powerlessness.