The concepts of center and extension are closely related. Center refers, on the one hand, to the physical location just below the navel, which is considered by many martial artists, yoga practitioners, and healers as the locus of a high concentration of energy. On the other hand, center refers to the sense of being balanced, grounded, based, or rooted. The Hapkidoist stands upright, with feet shoulder width apart, and hips rolled slightly to a position over the heels. In this alignment, the Hapkidoist feels centered, and feels his awareness sink down into his physical center.
Extension refers to the drawing out of someone else s center.
When an opponent lunges at a Hapkido practitioner, or attempts to hit or kick him, the Hapkidoist allows his opponent to become extended, or unbalanced. The Hapkidoist accepts the force and momentum of his assailant, and uses this energy to uproot his assailant. As his opponent becomes extended, the Hapkidoist becomes connected to his opponent. They move as one. There are many motions in Hapkido.