Therapists are required to maintain subjects' posture and move their center of gravity in body manipulation. Therefore, it is important to educate "the center" as the most important body sense for skillful body manipulation. The educated center dominates the support of bones, and enables the subject to maintain posture and move without excessive muscle activity. Moreover it is possible for a therapist to connect to the center of the subject through the contact plane for the educated center of gravity line as the subject's middle of the body in body manipulation, and then enable the manipulation of the body without excessive muscle activity.