Martial arts can be great cardio training, as you said a heavy bag will wear you out with a quickness. Grappling is another great workout, prior training is important. I just recently started doing sand bag workouts as highlighted here at ITS: Sandbags Unconventional Tools for Functional Strength
Lugging around that 80lb bag is great, its the first time I've been good and sore after a workout in a while.Â I started off very slow and deliberate a few weeks ago (really focus on good back position and lifting with the legs), just because the potential for back injury is high if you aren''t careful, and then turned it up a notch once I got used to the mechanics of the bag and my body got used to new motions.Just be sure to choose your filler wisely, I went with rubber mulch, but it is very coarsely ground so my bag is at the absolute limit with just 80lbs, so I'll need to ditch some of the mulch and add some sand or something to increase weight. Luckily sand is free and abundant in my neck of the woods -er desert.
Edited by spenceman, 07 July 2012 - 08:00 AM.