• 3.1 Posture of a Limb 
• 3.2 Posture of Other Body Parts

3.1 Posture of a Limb

For the posture column of the leg, the default notation uses the pelvis to establish a frame of reference, and treats the knee as the "pointer" for defining the direction of the gesture. For the arm, the default notation uses the chest to establish a frame of reference, and treats the hand (more precisely, the wrist) as the "pointer". These defaults may be overridden by appropriate notations. 

A limb (the arm or leg) has a base joint (the shoulder or hip), a middle joint (the elbow or knee), and a terminal joint (the wrist or ankle). The reference point for the pointer is usually the base joint. However, it is sometimes easier to describe the position of the pointer relative to another part of the body, such as the middle joint, the opposite terminal joint, the head, the chest, the waist, the pelvis, etc. 

Since both the middle joint and the terminal joint can move either up-and-down, or left-and-right, the limb has four degrees of freedom. This means that four spatial relationships among its parts are necessary to define its posture. These may be any of several combinations of bearing, distance, flexion, and rotation signs. These could be, for example: 

(a) the horizontal and vertical bearing of the terminal joint relative to the base joint, the degree of flexion of the limb at the middle joint, and the degree of rotation of the middle joint around the terminal joint-base joint axis. This is the default for representation of arm posture.  

(b) the horizontal and vertical bearing of the middle joint relative to the base joint, the degree of flexion of the limb at the middle joint, and the degree of rotation of the terminal joint around the middle joint-base joint axis. This is the default for representation of leg posture.  

(c) the horizontal and vertical bearing of the terminal joint relative to the middle joint, and of the middle joint relative to the base joint, 

(d) the horizontal and vertical bearing of both the terminaljoint and the middle joint relative to the base joint, 

(e) the horizontal and vertical bearing, and distance, of the terminal joint from the base joint, and the degree of rotation of the middle joint around the terminal joint-base joint axis. 

All of these posture notations, and others as well, are possible, however, the most common are (a) and (b) above. In case (a), a flexion symbol is placed even with the action stroke, a 3D bearing sign is placed above the flexion symbol, and a rotation sign is placed below the flexion symbol. The 3D bearing sign shows the bearing of the terminal joint (wrist or ankle) relative to the base joint, the flexion sign the degree of bending at the middle joint, and the rotation sign the degree of rotation of the upper limb. 

Collectively, the symbols which describe a single posture are referred to as a posture cluster or posture glyph. 

In the case of a step, the leg taking that step, the direction and length of the step, and the part of the foot making floor contact, are normally indicated in the appropriate action column of the leg staff, while the degree of flexion and rotation of the leg, and possibly the direction the thigh is pointing, are indicated in the corresponding posture column. When support is divided, a great deal of variety in leg posture is possible. 

3.2 Posture of Other Body Parts