Figures in Motion - Action Analysis for Animators - page 218

with the figure's balance being altered and adjusted throughout the action.
The body shifts from one stable state to another, less stable one and then
back to stability, with the body at times appearing to be completely off
balance. However unstable the figure is at any given moment in the walk,
however, the net result of a walking action is one of stability. Instability is a
necessary part of locomotion—so much so that it could be said that a walking
gait is little more than controlled falling.

By beginning to analyze the very familiar movement of the walk cycle,
breaking it down to its basic components, we reveal the full complexities of
the action. We can start to make sense of the different actions within a walk
cycle, first by dividing it into two distinct parts; the stride and the passing
position. In a full walk cycle, a figure undertakes these two separate parts of
the action twice, each corresponding to both the right and left sides of the
body. The illustration aims to explain this idea more clearly.

The Stride

The stride describes the position in the walk cycle when the legs are at their
most separated point. One leg is fully extended forward, the foot having just
made contact with the ground; the other leg is fully extended behind the
figure, with the foot maintaining contact with the ground but preparing to
lift. At this point the heel of the foot may be raised slightly from the ground.
During the stride phase of the walk cycle, the figure is supported by both legs.
The length of the stride varies greatly in a walk; the shorter the stride, the
more likely it is that the heel of foot in the backward position will be held flat
on the ground. We will see how these different component actions vary within
the various walks illustrated.

FIG 5.29 Walk cycle main key
positions. a: The passing position.
b: The stride.

(a) (b)