Consider for a moment a top athlete, dancer or musician, and you’ll realise that humans have the potential for incredibly accurate and coordinated movement. But what makes coordinated movement possible in the first place?

Despite being entirely unfamiliar to most people, two aspects of ourselves govern our posture and provide a foundation for all movement and balance. These are postural tone and body schema.

When these are functioning well, humans can reach ever greater heights of performance. But when they are functioning poorly, there are a number of adverse consequences such as muscle tension, malcoordination, poor balance, discomfort, pain and worsening mental health.

This article will define postural tone and body schema and then explore how they influence each other for good or for ill. Lastly, I will look at ways in which we can fine-tune them and so improve the way we function.

Defining postural tone

First, postural tone, or ‘postural muscle tone’, is the ongoing, low-level muscular activity that supports us against gravity and other forces. Postural tone is generated subconsciously, and differs from voluntary muscular activity such as clenching a fist or ‘standing up straight’. Most people are surprised to learn that for most of the time, maintaining a posture requires very low levels of muscle activity: typically between 2 and 5 per cent of the maximum force you might voluntarily apply to a muscle.

Healthy postural tone is fundamental to movement. Too much of it and movement becomes stiff; too little and our bodies collapse against gravity. Two characteristics of healthy postural tone are its adaptability, and its appropriate distribution through the body. Research has shown that individuals vary greatly on these two measures of postural tone.

The quality of postural tone can be adversely impacted by a multitude of factors such as everyday habits, our emotional state, and physical pain or injury. Furthermore, conditions such as camptocormia and Parkinson’s Disease lead to disturbances in postural tone.

Defining body schema

Next, the body schema is our brain’s map of our body parts in space. This internal map is continuously updated with sensory information (tactile, proprioceptive and visual) so that the brain can constantly track how the body is configured. The body schema is essential for planning and executing movement: in short, you can’t move somewhere else unless you know where you currently are.

The body schema includes information such as how long our limbs are, where our joints are, our range of possible movements and how our body parts are configured in relation to each other (e.g. are my legs crossed as I read this?). Part of the job of the body schema is to constrain action so that we don’t try to move in impossible or painful ways.

The body schema is by necessity holistic, or a map of the whole. The reason for this can be understood through a thought experiment involving a creature very different to us which we might call Scatty:

Imagine, for instance, that Scatty’s body consists only of two detached hands capable of independent movement, like the character Thing from the The Addams Family, but in duplicate. Scatty could do much that normally embodied subjects could not. She could rotate each of her parts 360° in a single plane in opposite directions, or simultaneously grab an elephant’s trunk and tail. By contrast, in our case, bodily actions are spatiotemporally constrained by the body itself as an integrated whole—when we move a body part, it will take as long as it does and involve the physical displacements it does, because that part is a part of an integrated whole.
de Vignemont et al., p.10

That said, the body schema is also malleable. First, it must adapt to enduring but slowly changing physical properties such as our size, joint flexibility and muscle strength. And as well as updating in real time to whatever position we’re in, it will even extend beyond our bodies to incorporate tools or vehicles so that we can safely judge their dimensions and effectively exploit their capabilities.

Like postural tone, the body schema is susceptible to unwelcome disturbances. These can be the result of conditions such as anorexia, dystonia or Parkinson’s Disease. Pain and injury will also alter this vital map of ourselves.

Finally, the conscious experience of the body schema is rarely discussed. I have written about it here, however.

The reciprocity of postural tone and body schema

At first glance, postural tone and body schema may seem like quite separate phenomena. However, they are deeply intertwined.

The set of illustrations below exemplifies this by showing how the quality of postural tone in the trapezius muscles could influence the body schema, and vice versa. Full explanations follow.

i) rigid postural tone causing inaccurate body schema.

A chronic contraction of the trapezius muscles causes long-term retraction of the shoulder blades across the back. With a lack of fresh sensory input from positions beyond this retracted state, the extent of the body schema atrophies. Over time, the body schema fails to map the available range of movement at the joints (particularly sternoclavicular and acromioclavicular joints) as well as the available volumetric space across the back and around the arms.

ii) inaccurate body schema causing rigid postural tone.

An inaccuracy in the body schema develops whereby the location of the shoulder girdle joints (sternoclavicular and acromioclavicular) are poorly mapped, along with the potential range of movement at these joints. Lacking detail for how and where to respond freely to internal and external forces, postural tone becomes unnecessarily rigid in the trapezius and other surrounding muscles. The internalization by the brain of cultural notions of good posture (for example, ‘shoulders back’) can be one cause of the initial mismapping by the body schema.

iii) adaptable postural tone causing accurate body schema.

When postural tone is adaptable, sensory input constantly updates the body schema from a wide range of positions. In this case, when the trapezius muscles are able to fully release as well as contract, the body schema is able to accurately map an appropriate range of motion at the sternoclavicular and acromioclavicular joints. With adaptable postural tone, the potential for greater volumetric space for the back and arms is recognized by the body schema.

iv) accurate body schema causing adaptable postural tone.

When the body schema is accurate, it maps in detail the location of joints, the dimensions of body parts and an appropriate range of movement for them. Being able to refer to this detailed map means that postural tone can adapt precisely and efficiently to the forces acting on the body. In this example, if the body schema accurately maps the location of and range of movement at the joints of the shoulder girdle, as well as the potential volumetric space for the back and arms, then postural tone can adapt in precise ways by exploiting those freedoms.

Improving postural tone and body schema

According to a recent scientific model, the Alexander Technique fine-tunes both postural tone and the body schema through intentional and attentional processes. Here’s a simplified version of the model:

The exact mechanisms are not known, but verbal and hands-on guidance are likely to have a beneficial effect on postural tone and the body schema. For example, on the one hand, Alexander Technique teachers will often help their students become aware of the location of joints and the range of movement available. This is likely to impact the body schema. On the other hand, Alexander Technique teachers seek to enable their students to ‘do less’ which is likely to reduce patterns of tension and create more adaptable postural tone.

Finally, one of the key skills of the Alexander Technique is Direction. Directions are self-instructions for restoring movement and coordination and are explored at length here. For now, it is interesting to note that different Alexandrian Directions tend to emphasize either postural tone or body schema. Below are some examples.

Emphasizing adaptive postural tone, we might have:

My neck is free

My shoulders are free

I am not compressing myself

I am not hunching my shoulders

And emphasizing an expansive or more accurate body schema, we might have:

Let the head float on top of the neck

My back is widening

The pelvis belongs to the spine

My spine is one

Think of the distance between the sternum and the edge of the shoulders

Further examples of Alexandrian Direction can be found in this article.

Conclusion

The condition of our postural tone and body schema can have profound consequences for our overall health, and yet so little useful information on this topic is available in the public domain.

That said, there is a growing body of evidence that the Alexander Technique nurtures these aspects of ourselves. The message for anyone who hasn’t tried the Alexander Technique is therefore: it can be life-changing.

Further information on taking lessons in the Bristol area is here.

Why your map matters: body schema and postural tone

Defining postural tone

Defining body schema

The reciprocity of postural tone and body schema

Improving postural tone and body schema

Conclusion

Further reading