Whichever martial art you decide upon, remember that your body must be in good physical condition to sustain the impact of repetitive techniques. And you have to recognize your limits. You can raise your limits but do so gradually or you will get injured.
One way to gradually improve your cardiovascular capability is to do the following drills continuously for 30 minutes: Focus on going from one technique to another as smoothly as possible. Start out slowly and gradually build up speed until you reach the fastest you can go while still maintaining good form.
Start with basic breakfalls; then move on to walking throws, emphasizing smooth entries over the actual throw. (Do three entries per throw) This will help make your Judo stand-up more fluid. If you really want to crank up your heart rate try speed throwing; maintain good form and try to throw each other as many times as possible in one minute. Use your favorite throw for this exercise.
Continue with groundwork; hold downs, chokes, arm / leg / neck locks. Flow from one technique to another in a continuous motion. Here, you will be looking to raise your heart rate, not lock the technique up tight or fight getting out.
Practice basic Karate blocks and punches while moving around, and finally conclude the training with an application of fluid jiu-jitsu self-defence techniques.
Contributed by: Sensei Michel Leblanc