LET'S FOCUS ON OUR CENTER.
Our physical existence subjects to the laws of the universe, and thus, the rules of physics as we know them. Motion (movement), stability, and balance are all natural and reoccurring parts of life (our existence), thus, they are also governed by the rules and principles of physics.
In physics, and "object" is anything with a mass that is greater than zero, including people. Every object has an imaginary center of gravity (COG) that represents the location of where the object's entire mass is concentrated. The object's COG us used to understand, estimate, and/or calculate the object's stability, balance, or tendency to move. The object's COG is not real, and does not actually exist physically in our body. In humans the COG "falls" about an inch below the naval, and in front of the second sacral vertebra, while standing in the anatomical position.
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The COG of an object "moves" as parts or the entire mass of the object moves. Furthermore, the COG follows where mass goes. For example, if a person lifts their arm upwards and outwards, the COG will move to a certain extent upward and outward compared to the natural location of the COG while in the anatomical position..
Another example would be a person with a backpack on their back. The backpack adds mass backwards and upward compared to a person's natural location of the COG while in the anatomical position. Thus, with the backpack, the COG will also move backwards and upwards. When a woman is pregnant, as the pregnancy advances, more mass is added to the front and lower area of the woman's body, causing her COG to follow forward and downwards.
If an object is in contact with the body, its mass adds to the body's mass, shifting the overall COG accordingly. Thus, we can manipulate our COG in multiple ways in order to either gain stability and balance or deliberately cause motion. manipulation of the COG is used for dynamic stability, dynamic balance, static stability, and static balance. Since the COG is an imaginary point, it can "fall" outside of the body, since it is not physically limited from "doing so". For example, if a person bend over touching the ground with their hands, their COG is will move forward and downwards to a point outside of the body.
The image above shows how the COG moves as it "follows" the addition of mass, or change of location of mass compared to the anatomical position. In all three images, the yellow dot estimates the original location of the COG prior to the change created to the object's overall mass. The red dot estimates the location of the COG after the change created to the object's overall mass.
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