Graphics Reference
In-Depth Information
shoulders, no longer providing the additional assistance to the movement,
will be much reduced. Of course, if the figure continues in this way it
becomes more effective to change the mode of locomotion altogether from
walking to swimming.
As we can see, the progressive movement of this walk involved a number of
alterations to the gait that were driven by the need to maintain efficiency of
movement in response to different environmental conditions.
FIG 4.9
The change of gait of a cat
from walking to prowling.
Our second example is that of a domestic cat prowling after its prey. Initially
the cat is sitting at rest in a fairly upright stance with its forelegs straight and
hind legs bent, enabling it to sit back on its haunches. On seeing its prey, the
attitude of the cat changes; it begins to prepare for the attack by stalking
the prey animal in anticipation of a rapid movement forward. The cat's front
legs bend, allowing its body to move downward, making a lower and far less
pronounced profile. As it does this its head pivots to maintain its view of the
prey. The front legs move forward in a single step; the rear legs stretch, lifting
the pelvic girdle upward. The cat's body now assumes a more horizontal
attitude. With its knees bent, the cat's shoulders are located almost directly
over its front feet. It has lowered its profile to remain out of sight of its prey.
Keeping low and moving slowly, the cat's movement is restricted to the legs,
with very little upward motion of the body. As the cat moves forward, the
