In Tang-soo-do, we get a moderate cardio workout doing marching drills and forms because we usually do them at a fairly brisk pace.
Sparring is a great conditioning workout for us, as is putting together combinations of strikes and kicks using bags and focus mitts, and groundwork classes offer a great workout as well.
Self-defense classes are more laid back (cardio-wise).
All in all, our system will get you into shape and keep you there if you're consistent and keep a decent diet.
I agree that the best way to go, if you're interested, is to try it out and see for yourself. If you like it, but the conditioning isn't what you hoped it would be, then you could do your conditioning between classes. (At the very least you should be stretching, even if you're not involved in a martial art at the present time).

Edited by choonbee (08/21/11 09:56 AM)
Insert profound martial arts quotes or tough guy phrases here.