Keep in mind that this concept must be applied throughout the character. The 50% I mentioned included all parts of the body. It’s important that you keep an equal distribution across that line regardless of the pose. This will ensure the character’s physical appearance is true to the laws of physics and appears natural and possible.

Asymmetry
Characters often gesture with multiple appendages. Both arms might rise in triumph from a victory or extend outward to embrace a loved one. They are striving for the same goal and often end up behaving alike. This symmetry can contribute to an unnatural pose, and make the character feel wooden and stiff. A slight adjustment can make all the difference.

Take the example of a character that has raised his arms protesting his innocence. He is about to deliver the line, “I didn’t do it.” Both arms extend from the body, and the elbows move in toward the torso. Figure 8 shows this gesture with both limbs in identical positions.

[Figures 8 & 9] The arms are symmetrical (left) in their raised position. The asymmetrical pose (right) is more appealing.

The pose is stiff and lifeless. It’s inconceivable to think that two arms could strike and maintain the exact same pose. By repositioning one of the arms, the gesture becomes much more natural. The character’s body has a sense of asymmetry and is more lifelike. (See Figure 9.) Although these examples involve static poses, it’s absolutely necessary to be conscious of symmetry when moving in and out of a gesture.

Watch for Twinning
When two appendages hit a pose on the exact same frame, it’s referred to as twinning. Arms, for example, often mirror each other’s action as they move in and out of a pose. It is highly unlikely that the human body could replicate this amount of symmetry while performing a motion. This movement is abnormal and helps to create an unbelievable character. A minor adjustment can make the flow between poses much more effective.

[Figure 10] The right arm hits at frame 15 (on left), the left arm at frame 18 (on right).