anyone ever do Cardio Kick boxin or a bag workout for cardio?

Anyone ever do any type of martial arts exercises to help with cardio? I see a few folks here that do Martial Arts like I do, and it is really relaxing and a great cardio exercise if you punch and kick a bag for 15 or 20 mintues. It is also good for power and strenght training (if you hit a bag like I do). we have a local gym here, with a 400 pound bag (a big Mofo). It is located in the basketball gym, when I put on my bag gloves and start rocking that thing, you can almost hear a pin drop. Afterwards, my knuckels are swollen and bleed sometimes, but my legs arms and body feels great.
Anyone else do this or I am the only Martial Art Nerd here?

I did that for a little while, but I always get carried away. I love hitting a hard canvas bag. The only problem is that I don't stop. When I do, I'm completely exusted, thus hurting my workout. Its good practice though. I mean, God forbid you do ever have to protect yourself or your family, you'll be ready to go. So many guys are huge, but don't know how to throw a punch. I don't know, I'm just babling now. Its better to have a bite thats worse than your bark.

Because I can't control myself I'll usually hit the bag after my workout.

I do a heavy bag a couple of times a week. Its a great workout. I tape up my hands and wrists so they dont get hammered. I keep it to 15 minutes otherwise my arms are tired the next day at the gym.