The practice of the Japanese martial arts is often connected to the practice of Zen. From a purely practical point of view, a mind that is not distracted by stray thoughts and is completely focused in the present is a mind well prepared for combat. The martial arts are often practised as a form of moving Zen. So it makes sense for anyone who wants to explore this aspect of karate to try their hand at Zen meditation. This is a nice introductory video.