What Is Balance? (COM and BOS)

Image courtesy of achievebalance.com

This is the second in a series of posts on balance.  There is a lot of information to cover with this, so if I missed something, it may be covered in a later post.  Otherwise, if you think it would be better-suited for today's post or if I didn't discuss something thoroughly enough, drop a comment below!

A few weeks back I wrote a post making an argument that balance exercises are challenging a skill set rather than a specific tissue and relating that to the rehabilitation process.  Let me back up for a moment and start by discussing what balance actually is.
Balance Defined

According to Dictionary.com, balance is a state of bodily equilibrium.  In RTS™ we discuss that physics dictates the need to keep your Center of Mass (COM) over your Base of Support (BOS) in order for you to keep from falling over.  The act of doing this is the gross outcome we see as balance.

Center of Mass (COM)

Image courtesy of seventeen.com

The exact positioning of your COM at any one point in time is largely dependent on how your mass is distributed at that moment.  Are you leaning towards one side or the other? Do you have one arm raised up overhead? Any slight adjustment in positioning will alter where exactly your center of mass is located.

Image courtesy of infochachkie.com

Funny enough, it is possible to have a COM that is outside of the mass of your body, meaning it is not contained within your physical structure.  An example of this would be when somebody performs the Fosbury Flop while competing in the high jump.  Generally speaking, in this video the COM of the athlete as he is over the bar is somewhere below his butt and between his head and his heals.

Base of Support (BOS)

BOS refers to the surface area of the outline created by all of the points of contact of you plus anything you are holding on to or touching and the ground, the plane of which is in opposition to the force(s) being applied.

In other words, if you are standing on one foot, your BOS is the outline of your foot.  If you are standing on two feet, your BOS is the outline of the outside of your feet plus the area between your feet.  If you are holding on to a chair, that outline would extend out to go around the edge of the shape created by the four legs of the chair.

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Additionally, based on the forces that are to be opposed--in reality you'd just be opposing the resultant of the forces instead of separate forces--the shape and surface area of the BOS will change.  Think about how you would adjust your feet if you were going to resist somebody pushing you from the front as opposed to pushing you from the side.  This is the difference I am talking about.

If your COM ever falls outside of your BOS, you begin to fall over.  Whether seated, standing, kneeling, or in any other position, if you start to tip far enough one way and/or if your BOS gets small enough, eventually you will topple.  When you are able to keep your COM over your BOS, that is the act we commonly see and call "balance".

What did I miss in today's post? Let me know below!

Your body.  Your training.

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