Kime refers to the mental and physical focus of energy used in karate. Let's look at the two type of kime and see how they differ:
Physical kime: The physical aspect of kime refers to the focus of physical energy created by one's body mechanics. This movement is used to concentrate the energy of an attack or defense into the actual karate movement. This power is generated by the body as a whole to create the maximum amount of energy into the karate movement. For example, the movement of the rear leg initiates the power of the reverse punch in karate. This energy is then carried to the torso through the rotation of the hip. The torso rotation adds additional energy to the punch, which transfers this energy to the arm, and eventually to the fist. The movement must be precisely controlled and timed throughout the body in order to generate the maximum amount of power. This precision and timing can only be developed through the repetition of training and watchful instruction.
Mental kime: The mental energy or focus is accomplished by focusing one's mind on the technique and timing being initiated without actually thinking directly about the technique. The mind controls the body yet the mind can not be preoccupied with the actual mechanics of the movement during the execution of the movement. The mind is focused on the uniting of the body and the mind to execute the movement. Through repetition, the part of the brain that controls the reflexive action is developed which controls the timing and execution of the movement. The conscious part of the brain does not focus on the physical movement but creates a state within the brain that allows the reflexive part of the mind and the body to maximize their communication thereby uniting mind and body. This unity allows the body to execute the technique with the precision and timing necessary to execute the physical technique with maximum effectiveness. The timing of the technique's execution is controlled by the reflexive action of the brain. The perfection of this timing develops with continual practice and repetition of the technique. Practice also enables one to attain this state of mind on command. Practice also allows for a greater unity between mind and body and thus more effective execution of the physical technique.
Development of mental kime allows the mind to push the body beyond their normal limits. It is said that the mind and body are normally using only a small fraction of their total potential. Karate training helps to tap and harness this unused potential. In addition, training allows one to know one's physical limits. This allows the mind to push the body in training and combat to the physical limits without "breaking the machine". Pushing beyond those limits can and often do lead to injury. It is said also that the mind tires long before the body. Training allows the mind to know the body's limits in regards to fatigue and push the body to the limits of physical exertion. Yet one may be put in a situation where one must push one's self beyond those limits to react to a situation which may require the push as in the case of reacting to a life-threatening situation.
Training by the same regards enables the karate practitioner to know the limit of one's own mind. The limits of stress and physical strain that the mind can tolerate become known. Karate constantly pushes these limits which enables one to know one's self both physical and mentally the longer one trains.
The ultimate goal in Karate is mastery over one's self.