Based on the following from the To slap the ground or not
Raul Rodrigo wrote:
(Post #94)/../My only addition is I'm still trying to understand what the "correct body mechanics" really is, and it will take me several more years to get anywhere./../
Aran Bright wrote:
(Post #95)What do you mean about opening up your joints? Say for example the elbow, do you mean to straighten if bent or extending along the length of the arm?
let me explain this. In principle, it's the same as any number of other descriptions pointing to how the body should move in a connected manner (say, the 4 principles Tohei devised and taught in the West), or as Mike, Dan, Rob and others promote as a way of using internal strength. As such it's as much a result as an effort to cause such. (For concrete training methods I suggest using the aikido misogi exercises and of course the actual keiko techniques, and exercises such as Robert John described (from Minoru Akuzawa) in the Training forum.)
Opening the joints is extension - in all directions. Opening all the correct joints (I'm not sure if there are some that remain closed) creates one point and weight underside.
Example: leaning against a wall. As one pushes, one would be surprised if the chest muscles tightened. But probably the elbow muscles are tight and the joint compressed. Effectively, one pushes against the elbow/forearm joint, not the wall. So, the shoulder joint is mostly open, but not the other arm joints. Now, one attempts to open up the elbow joint, either straight arm or slightly bent arm. A downward rotation of the elbow helps, and also opens up the shoulder joint more. If one pushes again against the wall one should now feel that one is pushing against the forearm/hand at the wrist joint rather than at the elbow joint. Using similar principles to open the wrist joint allows one to feel that one now pushes against the wall with the flat of the hand. And finally, if one continues to extend the fingers so that the hand joints open up, one may feel that one is pushing against the wall at the actual fingertips. So, one has brought one's pushing strength to the fingertips. Keeping the joints open despite pressure from various directions is hard, inward-directed work.
The basic idea is to keep such open joints already at the time of contact. A simple exercise is to slightly bend forward and pretend to pick up something a slight distance away on the floor with the fingertips, thereby extending the shoulder, elbow, wrist and finger joints. Then standing up normally again, this position of the joints is kept during the contact and subsequent movements. Think of extension of limbs and fingers as the way to open the joints rather than making a shape which needs to be preserved with hardness.
The same applies to the neck and back, hip, knee, ankle and toe joints, without whose action it will be impossible to really "sink" underneath the partner without moving at the point of contact and "lift" (or in some cases "sink/collapse") uke before the visible movements begin.
The trick is in keeping the joints open while moving the limbs in gross external motions (vertical changes via knees, rotation and lifting/sinking of the arms). For such, the limbs must be connected and powered by the center. Without the open joints, I think the power of the center cannot reach the extremities and control their motion precisely.