Ignatius Teo wrote:
As Shaun mentioned, joints can be opened/closed, or locked/unlocked. You can "lock" a person from their fingers to the toes (yubitori-waza is a good way to feel how this works - without the jujitsu type pain compliance). It gets really interesting when you "open" uke's joints and establish a path to their center, and they don't know what the heck you're doing and why they can't do any thing. And if uke closes a joint off (as in "resist"), the anticipated center of the movement changes.
What you are referring to hear is the principal of jiu, and has nothing to do with the principal of Aiki.
The principal of Jiu has nothing to do with pain. Jiu is the ability to move your body around force, to take no more force then you can comfortably manage and to redirect the force in a new way. Physical out reaching, feeling inside of someone's body via mechanical connection is part of Jiu.