One of the most important aspects of martial arts training is proper breathing. However, for practitioners of hard styles, effective breathing methods are often left to the students to figure out on their own. The central principle of breathing is of internal cleansing, getting rid of that which is old, worn out, and stale, and exchanging it for what is new, fresh, and energized. During inhalation we are bringing in fresh oxygen, nutrients, and vital energy. During exhalation we are expelling carbon dioxide and other toxins and poisons that we produce or collect in our daily lives.
Practically all karateka include kata practice as part of their training. The question asked by the vast majority is, "Why?" Certainly many karate practitioners slight the practice as they feel it is a pointless exercise that does nothing to increase fighting skill; "I hate kata. I'd rather spar!" is the 'macho' boast made by many a misguided junior grade (and sadly a few senior ones).
Kata are also used to grade students, a black belt sometimes has to perform every single kata they have learned to illustrate their mastery before being graded. One single misplaced foot or a loss of balance can make the difference between a good kata and a great kata!
Kata isn’t only to help you perfect the physical motions, in fact, many martial artists perform katas not to improve themselves so much physically as to increase their inner awareness of their own person and how to improve their skill with a purity of mind and body.