Centre of Gravity
The centre of gravity of any body is the point about which the weight is equally distributed. It is the point about which the force of gravity acts upon. And, in the human body, this point is usually the naval.
Static balance is dependent on two contributing factors. These are the centre of gravity, and the base of support. As long as the centre of gravity is kept within the base of support, the body will be kept balanced. Each of these factors can be manipulated, in order to increase or decrease the body’s ability to remain balanced.
Changing the position of the centre of gravity can increase or decrease the body’s stability. A lowered centre of gravity results in greater stability than a higher one. And, shifting the centre of gravity towards the edge of the base of support will increase the chance for instability.
Changing the size of the base of support will also affect the stability of the body. A larger base will increase stability, while decreasing the size of the base will result in a less stable system.
The body does not only need to be balanced when static. It also needs to maintain balance when in motion. During any movement, the centre of gravity will always be moving. It will not only move relative to the base of support and height from the ground, but it will also change position within the body itself.
This change in position will obviously mean a change in stability, throughout any movement. And, depending on the movement, this can either be a good or a bad thing. Movements being done in one place (squatting, for example) will require the centre of gravity to be kept within the base of support, as it moves. Excessive lean in any direction may lead to a loss of balance, and potentially injury. On the contrary, movements that require a change in position (such as walking and running) rely on the centre of gravity moving outside of the base of support to cause movement in the desired direction of movement. In these instances, balance is repeatedly lost and regained, as the base of support is moved to recapture the centre of gravity, each time the centre of gravity is moved out of the previous base of support.
Defined as the body’s awareness of joint positioning in space, proprioception is the sensory function which allows the body to maintain balance and stability. This falls under the control of the autonomic nervous system, using signals from organelles such as muscle spindles and golgi tendons, as well as other sensory perception organelles within the joints themselves, to establish a dynamic picture of where any body part is, in relation to the rest of the body at any time. An example of this would be sitting with your feet under your chair, when at a table. You can’t see your feet. Yet, you know exactly where they are.
The body uses this sense of positioning to maintain balance in every state of motion. And, like all other systems involved in movement, it can be trained, and improved.