The Posture-Balance Connection Part 3.

The Posture-Balance Connection is our Education, Coaching and Rehabilitation framework for helping people with problems of spinal pain, mobility, and balance.

Through this framework, I explain how it is that we are able to maintain ourselves upright and move with comfort and efficiency; what happens when the postural system which is tasked with keeping us upright starts to fail, and what the consequences are, and what we do to address it.

There is a lot of information here which I have separated into a 4-part series represented as four key principles.

In the first article in this series, ‘The Posture-Balance Connection’ I discussed how the ability to shift our weight enables us to hold ourselves upright and orientate ourselves to our task at hand.

In the second article (The Postural Deterioration Cycle), we looked at what happens when this starts to fail. In this article, we will explore how we examine weight-shifting efficiency and what this means for the rehabilitation of chronic spinal pain, our mobility, and balance.

The third principle in the Posture-Balance Connection is:

“For rehabilitation to be effective, we must be ABLE TO MEASURE weight-shifting efficiency.
In this article, we are going to explore what happens when this starts to fail.” 

In The Posture-Balance Connection article I used the example of a skater to describe how they manipulate their centre of gravity in order to both keep themselves upright and to generate movement across the ice.

To know how stable someone is and how efficiently they are able to move we need to be able to measure their centre of gravity from moment to moment.

Centre of gravity is very hard to measure, but we can see the effects of it quite easily in terms of how it’s projected to the ground by measuring the area in which weight-shifting occurs when we are standing still, and how efficiently we weight-shift when we are required to orient ourselves to a target.

We do this by using a very accurate weight scale that measures not just the amount of downward pressure but also traces movement over time. This scale is called a posturographic pressure plate and is used in research to measure stability.

A posturographic pressure plate enables us to measure any movement that we can translate into a vertical plane. There are three metrics that are particularly relevant to measuring stability and mobility.
1. Postural Sway
2. Limit of Stability
3. Weight-Shift Targeting

Measuring Postural Sway
Because we stand on two legs we are inherently unstable, we must make continues postural compensations to keep ourselves upright.
Postural sway is the result of the involuntary, compensatory movement our centre of gravity makes in order to keep us upright over our feet. It is measured in terms of the area that our weight shifts on the plate. The smaller the area, the more stable we are.
The test we use is called the modified Clinical Test of Sensory Interaction in Balance (mCTSIB) and it is the Gold Standard for testing stability.
In addition, we use this test to assess the constituent parts of the postural system under different conditions to see what increases and decreases postural sway. This means that we can use it to diagnose how stable an individual is, what specifically is affecting their stability, and how their stability changes under differing conditions.

Every person has their own postural character and mannerisms. Measurement of how they respond to different challenges enables us to create very specific and individualised rehabilitation and to get immediate feedback as to how effective it is.
Now this can be very valuable for anybody with a problem of movement, but particularly for people with chronic spinal pain, balance problems and movement disorders.

Measuring Limit of Stability
In terms of generating movement, we need to know how far an individual can project their centre of gravity, and how efficiently they are able to do it.

We can see how far they are able to project their centre of gravity in terms of measuring how far they are able to move on the plate without falling over. Typically, we measure eight positions around a clock face to generate a map of Limit of Stability. The map gives us the size as well as the directions an individual is having difficulty moving in.

Returning to our ice skater in the Posture-Balance Connection article, we explored how driving our weight forwards changes our centre of gravity and creates momentum. As our Limit of Stability drops, our ability to create momentum drops. We can observe this with difficulty getting out of a chair (it’s not just leg muscle strength, it’s the ability to drive yourself forwards), and in the ability to stride out.

A step is actually a result of a controlled fall.

We fall forwards and we catch ourselves with each step. As our Limit of Stability drops our step gets shorter, and if it gets short enough, we require an external device (a stick or a walking frame) to artificially increase it.

In the Posture Deterioration Cycle article, we explored how part of the process of deterioration is that our centre of gravity moves backwards and our weight shifts onto our toes so that we don’t fall backwards. This limits our ability to project our Centre of Gravity forwards.
Together increased Postural Sway and decreased Limit of Stability are the metrics of postural instability.

Measuring Weight-Shifting
Whilst postural sway and limit of stability provide us with metrics of postural instability, weight-shift targeting provides us with the metrics of movement.
We can measure how efficiently an individual is able to shift their weight in any given direction by giving them a target to aim for on a computer monitor. We can set up different targets in different planes of motion and compare.