What's wrong with a gun?
Feeling stressed out? Go "Postal."
Need exercise? Run from the cops after a shooting.
Just KIDDING, folks! I don't know much about martial arts except there are two general schools: "hard" and "soft." The "hard" forms are tough on the joints and bones - a lot of stress for both. The "soft" has less to do with strength and more with flexibility, balance, using the opponent's momentum against them, etc. Either one will put you in tremendous shape.
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Next time I send some damned fool, I'll go myself...