September 2, 2019
Pondering Postural Control: The Proprioceptive System
Proprioception = the sensation of body position and movement
Our sense of proprioception is a (mostly) unconscious piece of our perception of our body’s position. It involves information from mechanoreceptors in our muscles, tendons and joints: muscle spindles and Golgi tendon organs (GTOs). This information provides a constant monitoring of the position of our joints for functional movement – anything from standing on one foot to writing your name.
Proprioception is commonly thought of as contributing to a person’s ability to balance on an unstable surface. However from a developmental sense there is so much more to this sensory system. According to Ayres Sensory Integration, proprioception, when combined with tactile input, helps build the somatosensory cortex – the “map of me” as my friend Kim Barthel refers to it. If a child has a proprioceptive deficit, their internal sense of their body (=body scheme) is disrupted and therefore so is their ability to move efficiently in space. And of course, the proprioceptive system is best friends with the vestibular system; combined these two systems gives us a complete sense of where we are in space in relation to ourselves and our environment and also in relation to gravity.
There are standardized tests for proprioception. The Comprehensive Observations of Proprioception (COPS) was developed by Dr. Erna Blanche to identify proprioceptive issues in children with developmental disabilities. Observation categories include alignment, weight bearing/weight shifting patterns, postural control, force grading, motor planning, movement fluidity and mid-range control as well as behavioural observations (tends to enjoy hanging, pushing, climbing, crashing, falling, bumping into others). So we can see that proprioception is implicated in so much more than just being able to balance on uneven surfaces. Unstructured observations can also be extremely helpful – does the child seek movement/avoid movement, navigate obstacles well, can they imitate limb positions and match movements, do they demonstrate quality co-activation of muscles around their joints, do they over-use their vision to direct movement? All of these can give us important clues about how a child uses proprioception.
Proprioception can also have a significant impact on our emotional arousal. Children with hypermobility often experience challenges with anxiety. It is hypothesized that in those with hypermobility, the joints send signals regarding the threat of pain to the brain, resulting in increased emotional arousal. Using proprioceptive input can also decrease emotional arousal; we often see this in the clinic as children will participate in challenging activities but then need to bump/crash/jump to assist with management of their arousal.
Proprioception can be a powerful tool. Proprioceptive input can be alerting/organizing for those children who have difficulty organizing their body for learning. It can also be calming for those who are sensitive to sensory stimuli. Dr. Temple Grandin developed her “hug machine” as a method to give herself proprioception through deep pressure which she used as a means of regulating her emotions and modulating her behavioural responses. Again, the approach in therapy is not to passively give proprioceptive input (although you can do this through passive joint compression) but to have the child actively engage in proprioceptive-rich activities (often referred to as “heavy work”) and use the optimized and integrated input in a meaningful activity.
Ultimately proprioception allows us to have a good grasp of where our body parts are in relation to each other and in relation to objects in our environment. It’s a key ingredient of both the stability and orientation components of postural control. Proprioceptive input also supports the modulation of other sensory systems and our emotional arousal. Ultimately this creates coordinated and efficient movement for function.
Next up in our series: The Visual System.