I believe cardio is the most imortant part of any self defense. I don’t care what fighting style you use, if you get winded in 10 to 20 seconds your in trouble. The fatigue starts before the first punch ever gets thrown. When your adrenaline starts to pump at the first sign of danger your breathing and heart rate increase. It is the bodies natural instinct for fight or flight. If you have been around many street fights you know they don’t last more than about 15 to 20 seconds after the first punch gets thrown and both people are usually sucking wind when it’s over.