PHASES OF MOVEMENT OF A QUICK WALK.
Four phases complete a step.
Contemplating the arms only, it will be perceived that they keep up a constant alternate swinging back and forth. The point where they pass each other will be when they both have approached their respective sides of the trunk. This particular moment when the arms are opposite one another and close to the trunk, or at least near the vertical line of the body, is coincident with the phases of the lower limb movements when one is nearly rigid as it supports the body and the other is at its median phase of the swinging movement.
These middle positions of the four limbs—the lower near to each other, and the upper close to the body—is a characteristic that should be taken note of by the artist. It illustrates, in connection with the extreme positions, certain peculiarities of motion in living things, in general. This is a sort of opening movement following by a closing one. These reciprocal changes, expansion and retraction in organic forms, symbolize the activity of life.
In the human body, for instance, during action, there are certain times when the limbs are close to the trunk and at other times when they are stretched out or extended. This is adequately made plain in jumping. Specifically: in the preliminary position before the actual jump, the appendicular members bend and lie close to the trunk. The entire body is compact and repressed like a spring. Then when the jump takes place, there is a sudden opening as the limbs fling themselves outward.
A rower in a shell plying his sculls exemplifies this phenomenon of a spring-like closing and expansion. In this case there is also a typical example of reciprocal compensating movements in the two pairs of limbs. When the rower leans forward and the arms are extended ready to pull on his sculls, the lower limbs are flexed and in contact with the front of his trunk. Then when the sculls have been pulled back and he has reached the other extreme position, the arms are flexed and close to his chest, while the lower limbs are stretched out straight.
A SUCCESSION OF ALTERNATE CONTRACTIONS AND EXPANSIONS CHARACTERIZES MOTION.
If the animator is planning to walk a figure across the field of the screen, there is one matter in the representation that he punctiliously takes heed of. It is this: to have the trunk rise as it is in turn supported upon one rigid leg and then upon the other, and to show that it falls slightly when the two limbs are outstretched at their extreme positions. In this alternating rise and fall of the trunk in walking, the head can be observed as describing a wave. The highest point of the wave is when the trunk is supported on the rigid leg and the lowest point when both limbs are stretched out as if flying from the vertical of the body.