Stability versus instability: The human body is unstable and made for movement. Part 2

Another important aspect of the principles of human movement is that we can easily change our base of support. The base of support is the area beneath a person that includes every point of contact the person makes with the supporting surface. In standing, it would be our feet and the area between them. In sitting, it would be our feet on the floor, our pelvis and upper thighs on the chair and, if we are leaning on the back of the chair, the area of our back that is touching the chair. The bigger the base of support the less effort our muscles have to make to keep us upright and the more comfortable we generally feel.
Think of the difference of standing upright for half an hour without moving much, versus sitting on a chair, versus lying on the floor. When we are standing up, the entire weight of our body is balanced on our two feet and we usually become uncomfortable in this position quite quickly, and may start fidgeting, or wanting to move around. The act of standing can be perceived as quite a lot of effort for the body.

In sitting our base of support is wider, as described above. In lying down, our base of support is nearly the whole body, not including the spaces between the back of the body and the floor, such as the curvature at the back of our neck, the curvature of our lower back, the area behind the knees and the spaces slightly above our ankles. As our base of support widens, our level of comfort increases but our freedom of movement decreases. Moreover, to get off the floor and start moving in a specific direction requires a lot more energy than moving in a specific direction when we are already standing. So, the bigger the base of support the less work the body has to make, the more comfortable we feel but the more our range of movement is limited.
Simply put, there is a clear trade-off between our freedom of movement and our ability to react swiftly to any situation, and the size of our base of support and our perceived level of comfort.
You can experiment with all these principles in my video lesson called: “The Human body: Some principles of movement”. You can also learn about the base of support in sitting, in my video lesson: “Better sitting in 10 minutes”.