Understanding Movement
"Posture should not be considered a static phenomenon. Even while people stand or sit still, there are inevitable small flucutations in their positions, or posture. Postural positions are maintained within ranges of movement." Whiting and Rugg, Dynatomy, p. 143.
IIn the standing body, there is an evolutionary imbalance in the pelvis that enbables the body to de-center itself and move in any direction without any thought at all. It is part of our ancient "fight or flight" reflex.
Although the body has a natural alignment that lets it function at ease, this alignment is naturally imbalanced. The spine compresses down and to the rear, and the femurs hold the body up to the front. This imbalance makes the area a rotational lever that enables us to move easily, since we can easily decenter ourselves. This is one reason why it is hard to stand still, but easy to move.
"Organized movement is possible only when loss of balance of the mass, or shift of the center of gravity, may be initiated from within the mass and recovery instigated through the same mechanism. Leverage and oppostion of parts are indispensible requirements." Mabel Elsworth Todd, The Thinking Body, p. 205.
The fulcrum of the lever is the hip joint (red circle). The lever is the pelvis (red arrows), with the force coming from the base of the lumbar vertebrae and/or sacrum, depending on the angle of the upper body and the muscles used.
The heads of the femurs are not perfectly aligned sideways in our bodies. They are angled slightly forward from the line of the femur itself (image to left).
The offset between the spine and hip sockets allows us to move forwards or backwards quickly, while the angles of the femur heads let us decenter and pivot immediately to the left or right.
These two structural offsets coupled with our major muscle groups give us a strong ability to move quickly in any direction from a rest, while also letting us change direction quickly while in motion.
Click here for another image of the hip joints that are lower and more forward than generally thought.
Images from Susan Hall's Basic Biomechancis
Posture, too, is dynamic and not static, with the underlying of premise of posture being the ability to balance and move in a constantly varying environment.
Here is a diagram of the factors involved in balance.
from Ski-and-ski.com
On the right, we see the whole body in its naturally evolved alignment: central axis, hip sockets, thighs, knees, lower legs, ankles and feet.
The entire structure can move in any direction instantly. It also supports the head, with its eyes, so they can coordinate with the hands.
Coupled with speech, hand/eye coordination gives humans a tremendous evolutionary advantage.
