“I have a back back”
When someone says, “I have a bad back,” it often reflects much more than a description of musculoskeletal pain or pathology. This labelling implies that there is a strong internal model that is formed through prior experience, where the back is perceived as being vulnerable or damaged.
Consider how you navigate the world, and your knowledge and beliefs about safety versus danger. This is all based upon previous experience, beliefs and expectations. These ‘priors’ are our brains attempt at protecting us from danger and ensuring that we can navigate the world safely and efficiently. This information forms our internal model and how we perceive the world. Many of the things that we do in our day-to-day lives occur in our subconscious mind. If we needed to think about the sequencing of muscles on every step of a walk, it would be very difficult and incredibly exhausting! But this highly complex task occurs without conscious awareness and is based on previous experience and expectation that is compared with the actual sensory information from within our body and the environment.
According to predictive processing theory, the brain functions as a prediction machine (Clark, 2014). It continuously generates top-down predictions about the body and our environment, and it compares this information with incoming sensory signals. In this framework, the belief of a “bad back” becomes a dominant prior, and a prediction that lifting or bending the spine, will lead to pain or injury. Even before movement occurs, this belief influences perception and behaviour by anticipating threat, and promoting protective strategies, such as avoidance, changes in muscle activation, and pain.
Our brain is making constant comparisons between the actual sensory information and our internal model. When a person has strong priors, there is more weight/trust placed on their internal model than the actual sensory information. Consider the examples of people who have a strong belief that the structure, such as a bulged disc, is the cause of their pain, but you have most likely been able to help people reduce or even resolve pain without any structural change…
To give you an example, while getting off the SkyBus at Melbourne Airport, I offered to help a lady get her suitcase from the storage rack. She responded, “Yes please, I have a bad back.” This moment illustrates how internal models that may be influenced by a previous episode of pain, fear of injury, and emotional responses, can shape our behaviour. This label of a bad back highlights the story that she has constructed about the integrity of her back. Even before attempting the lift the suitcase, her brain was simulating the potential outcomes that are influenced by her previous experience. This memory is tied to an emotion of that previous painful experience, resulting in a prediction that lifting the suitcase will hurt again. This internal model influences behaviour that may include changes in muscle activation, movement strategies or create avoidance. Furthermore, if lifting the suitcase does cause pain, this will then confirm that the internal model is correct, reinforcing those beliefs or priors. However, the opposite can also be true, and this is called a prediction error.
A prediction error occurs when there is a mismatch between expected and actual sensory inputs. When this mismatch occurs, it can update the internal model to align with the actual sensory information, and this is a constant and dynamic process. Unfortunately, in persistent pain, these prediction errors are not detected, as there is more trust placed on the internal model compared to the actual sensory information, therefore reinforcing this cycle. When a person’s internal model is shaped by fear, or negative beliefs, even non-noxious sensory information can be interpreted as threatening, leading to heightened pain sensitivity. Consider how language, imaging, diagnostic labels and even Dr. google can influence a person’s internal model.
It is important to remember that the brain is not a passive organ that waits for sensory information to arrive and then responds to this information. If a person expects or predicts pain, consciously or sub consciously, this can produce the experience of pain. If you ask a person with persistent low back pain to pick up something from the floor, or a person with shoulder pain to reach over their head, movements are altered prior to any incoming sensory information in the expectation of pain. Some will even say, “No, I can’t do that because it will hurt my back.” In some people, simply the thought of a certain movement or position can produce the experience of pain. This is the brain working as a prediction machine.
If we consider how this relates to manual therapy, perhaps we can use manual therapy as an opportunity to update a person’s internal model by providing a non-noxious sensory input in a safe environment, that creates a prediction error signal in the brain, thus, providing a window to update a person’s internal model. This may also assist to disassociate a movement with pain, as we often see with active soft tissue and joint mobilisation techniques. It may also provide an opportunity for graded exposure by gradually exposing a person to an uncomfortable stimulus, therefore reducing fear and promoting safety and reassurance with movement. Additionally, providing education to our patients about pain, and challenging negative beliefs is another important component that can provide a software update to the brain!
This software update is the incredible neuroplastic capabilities of our nervous system!
