If you were to describe the sensation of back stiffness you might use words like creaking, cracking and popping.
New research reveals this innate tendency to connect sound (or sight or smell) with sensation could change the way experts understand and treat lower back pain, a problem that affects 80 per cent of us and is the world’s biggest contributor to disability.
Back pain experts already understood that physical pain goes hand-in-hand with perception; if we feel safe our body relaxes, softening our perception of pain whereas if our body senses danger it protects itself by amplifying our perception of pain.
For the paper, published in Nature journal Scientific Reports, Dr Tasha Stanton wanted to explore this concept further to see whether engaging our sense of sound could influence these perceptions.
“We thought that adding sounds that either increased or decreased the need for protection would impact people’s protective responses for their back,” said Stanton, a senior research fellow from The University of South Australia’s School of Health Sciences. “And, indeed, this is what we found.”
When they applied pressure to the spines of participants while playing a creaky door noise, people were more protective of their backs and believed the pressure being applied was greater than it was. When they applied pressure while playing a gentle whooshing sound or a noise that became less creaky over time, participants were less protective and believed the pressure being applied was less than it was.
“Critically, these changes in perception relate very well to feelings of stiffness,” Stanton explained. “The more you overestimate force, the more stiff you feel and vice versa. In contrast, we found that actual objective measures of back stiffness [mechanical stiffness] do not relate at all to how stiff the back feels.”
It is this mismatch between mechanical problem and pain perception that has researchers intrigued and has significant implications for the way pain is treated.
“For example, if you sprain your ankle, the nervous system gets information from specialised receptors in the injured tissue,” Stanton said. “This danger message is sent to the brain and most often results in a feeling of pain. However, if you sprain your ankle while being chased by a bear, often you won’t feel ankle pain, because other relevant information [needing to run to stay alive!] is present that can override the danger message that is coming from the injured ankle.
“Thus a sensation is never really only mechanical or only psychological – both features play a role whether the pain/stiffness is acute [just happened] or chronic [has been around for ages]. As things get more and more chronic [especially with pain], there is more of a shift away from the mechanical factors playing a large role.”
This is where our perception of danger or safety plays a part in whether the pain sticks around. For example, seeing an MRI showing degeneration or disc bulges “puts your nervous system on danger alert” and increases the pain.
“Having this picture of damage in your head may change how you move and what you do and may impact your pain,” Stanton said. “However, what people don’t know is that if we imaged the backs of people over the age of 50 who do not have any back pain, 80 per cent will have evidence of degeneration and 60 per cent will have evidence of disc bulges.”
So soothing the senses of someone in pain can change their perception of their back and potentially relieve pain.
“In some people with back pain, an important part of treatment is increasing their knowledge about pain,” Stanton explained. “They may hold beliefs that any increase in back pain means that they have further injured their back. However, we know that the nervous system can become sensitised. Thus the increases in pain can merely reflect an increase in sensitivity of the system, and thus not relate to more damage of the back at all.”
Reassuring people in this instance can thwart the danger cue and calm the nervous system response, resulting in pain relief.
“There is much more to sensations of pain and stiffness than just the anatomy and function of the back itself,” she said. “Understanding how the nervous system reacts to different things and how this reaction affects sensations such as pain and stiffness is critical. My research is extending these ideas to feelings of back stiffness – what can we do to decrease the danger/increase the safety to reduce feelings of stiffness?”
About three million Australians take opioids despite the fact that they have been found to be ineffective for back pain. Instead, Stanton believes that engaging the senses could provide an alternative, more effective option for those suffering.
“If we can further understand how sound shapes feelings of stiffness [and potentially pain], then we can start to develop ways to use this in treatment,” she said. “Developing new treatments for back pain is a huge priority given the real problem that we are seeing with opioids in Australia [and the lack of effect of these drugs].”