Jeet Kune Do : physical conditioning

In Jeet Kune-Do, physical conditioning is a must for all martial artists. If you are not physically fit, you have no business doing any hard sparring. To me, the best exercise for this is running. Running is so important that you should keep it up during your lifetime. What time of the day you run is not important as long as you run. In the beginning you should jog easily and then gradually increase the distance and tempo, and finally include sprints to develop your 'wind.' Let me give you a bit of warning: just because you get very good at your training it should not go to your head that you are an expert. Remember, actual sparring is the ultimate, and the training is only a means toward this. Besides running, one should also do exercises for the stomach — sit-ups, leg raises, etc. Too often one of those big-belly masters will tell you that his internal power has sunk to his stomach; he's not kidding, it is sunk and gone! To put it bluntly, he is nothing but fat and ugly.
- Bruce Lee