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.