In karate, repetitive practice is a prerequisite to attaining proficiency in the art. Only through repetition can the movements in karate become automatic. Attacks are blocked without actively thinking about the attack and the block being used to defend one's self. Constant regular training allows for offensive techniques that can be delivered with almost no thought and with precision timing.
In the brain there are 2 main parts that we refer to when we talk about the basics of karate and how the brain relates to these parts. The first part of the brain is near the base of the brain and is composed of the spinal column and the primitive part of the brain that is utilized primarily for motor skills and reflexive movement. The other part is the more developed part of our brain that is used for reasoning and thought processes. This is the analytical and problem solving part of our mind where concepts and ideas are born and karate techniques are learned.
Karate strives to develop the reflex action through repetition of movement. When an attack is delivered, one does not have time to think about what attack is coming, what block should be used, and what counter attack should be delivered. With proper training, all three of these things are automatically computed and initiated by the brain in a split second.
Repetition of the basic techniques is what allows the karate movements to be executed without actively thinking about the movement. Repetition of techniques with a partner allows for the attacking and defensive movements to over time be delivered automatically.
At first, the brain slowly tells the body exactly how to move. As the movement is practiced over and over again the synapses (electronic pathways) between the reasoning part of the brain and the reflexive part of the brain improve. When this happens, communication between the body and mind improve and the body's reflexes become faster the more the movement is practiced. The conscious mind takes a less active role in the dictating of the body movements and reactions and the sub-conscious takes a larger role. Repetition with a partner practicing different technique allows for a reflexive reaction to be developed against an attack or defense for the techniques that are practiced. The more techniques and the more repetitions that are performed allow for a reflexive reaction to be delivered in more diverse combat situations.
When a high level of karate proficiency is attained the mind can then go into a state of "mushin" or no mind. This is the ultimate level of the unison of mind and body where the body is in total harmony and synchronization with the mind. This allows the karateka to automatically tap their arsenal of techniques, with minimal interference from the conscious mind. This allows for almost instant action and reaction.
Repetition becomes a spiritual exercise over time. When the true benefits of repetition becomes realized to the karateka the exercises then become spiritual exercises instead of purely physical ones. The movements cease to become boring and the true essence of karate-do emerges.