Follow through and overlapping action

These closely related techniques help render movement more realistic, and give the impression that characters follow the laws of physics. "Follow through" means that separate parts of a body will continue moving after the character has stopped. "Overlapping action" is the tendency for parts of the body to move at different rates (an arm will move on different timing of the head and so on). A third technique is "drag", where a character starts to move and parts of him take a few frames to catch up.^[12] These parts can be inanimate objects like clothing or the antenna on a car, or parts of the body, such as arms or hair. On the human body, the torso is the core, with arms, legs, head and hair appendices that normally follow the torso's movement. Body parts with much tissue, such as large stomachs and breasts, or the loose skin on a dog, are more prone to independent movement than bonier body parts.^[19] Again, exaggerated use of the technique can produce a comical effect, while more realistic animation must time the actions exactly, to produce a convincing result.^[20]
Thomas and Johnston also developed the principle of the "moving hold". A character not in movement can be rendered absolutely still; this is often done, particularly to draw attention to the main action. According to Thomas and Johnston, however, this gave a dull and lifeless result, and should be avoided. Even characters sitting still can display some sort of movement, such as the torso moving in and out with breathin