To develop sensitivity skills, we must improve the way the mind processes information. The mind receives information from the senses, processes it, generates a response, and then directs the body to produce a specific action. In Wing Chun, they use a sensitivity exercise called chi-sao or "sticky hands." In this exercise, practitioners remain in constant contact, and engage in a series of simulated attacks and counterattacks. The purpose of chi-sao is not to hit your partner, but to develop sensitivity to a variety of motions and to feel weaknesses and strengths in each motion. A chi-sao practitioner may detect forearm tension, shoulder tension, and overall body stability just simply by using touch. The energy used by the practitioners should be supple and flowing, without abrupt stoppages and mechanical motions. The chi-ao practitioner must respond in a strong yet relaxed position, still sensitive to the changing nature of his partner's position.
After detection of the opponent's intentions, the mind must process the information and generate a response. The greater the number of responses available, the more difficult it becomes to select just one, so it is best to have only one effective response for each attack situation.
Once the mind selects an appropriate response, the body must physically execute it. Different muscle groups must be trained to act as a unit to execute the response properly. This means endless hours of practice with a variety of partners against a variety of attacks. Developing sensitivity is not easy. Training the body is a must, but it is actually the easiest part of the training. Like everything else in Taekwondo, sensitivity training is 90 percent mental and ten percent physical.