Most of us have heard it all our lives; ‘sit up straight and don’t slouch’. Ergonomics has been a buzz word within workplaces for years; lumbar support in your desk chair, having your computer screen at eye-level, correctly adjusted chair height. But with the arrival of mobile phones and laptops, we find ourselves looking down while walking, slouching through the day at our desks (or maybe in bed, if you’re working from home!), and curling up on the couch in front of the TV each night.
Forward head posture has become common, and our advancing technologies may have contributed. While we may never know how much can truly be attributed to modern technology, this postural abnormality is thought to adversely affect the spinal cord. When the head moves forward it increases the weight on the spine, approximately 10 pounds for every inch moved. The increased weight causes an increase in the force on the spine, potentially leading to nerve irritation and cervical radiculopathy (inflammation of nerve roots in the cervical spine).
Cumulatively, this places an abnormal amount of stress on postural muscles, particularly the deep cervical muscles which are connected to the dura mater of the spinal cord.
It seems obvious why this would be of concern to chiropractors, and people under chiropractic care. But beyond the cosmetic, pain-related or ergonomic concerns of forward head posture lies a far more deeply seated issue: research is beginning to reveal that forward head posture may be linked to slowed central somatosensory conduction time, which affects the reaction time required to perform and learn new tasks and activities. The importance of reaction time is not isolated only to learning, but can be a good measure for processing any task as the decrease in reaction time is usually accompanied by a reduction in processing speed.
Given that the term ‘somatosensory’ essentially means the body and the senses (thus incorporating body and brain systems), what then is biofeedback and how can it help?
Biofeedback is essentially a self-learning intervention that helps people modify their ability by themselves. Biofeedback devices can therefore be used to correct abnormal posture (think of posture correction devices or exercises) or movements. The last randomised controlled study (published in the Journal of Chiropractic Medicine) proposes that a decrease in central somatosensory conduction time might have a positive effect on reaction time. Thus, the purpose of the study was to examine the effect of 8-weeks of biofeedback exercises on reaction time and central somatosensory conduction time in patients with forward head posture and cervical radiculopathy”
Now, chiropractors check and adjust for subluxations. That is the central theme of the profession. However, in order to correct severe postural issues, many chiropractors suggest the use of biofeedback exercises or devices to complement the effects of chiropractic care and aid the posture correction process. Thus, this study holds much potential insight for chiropractors and their practice members.
So, Let’s Look at the Study
To investigate the relationship between forward head posture, reaction time, and somatosensory conduction time, a double-blinded randomised controlled trial was conducted.
Initially 80 participants were assessed, before 10 were excluded for various reasons including not meeting the inclusion criteria. This left 70 patients with forward head posture and cervical radiculopathy, aged between 40-60, as the sample size for the study. The outcomes of the study were assessed through the following:
- Reaction time was assessed through a computer-based game in which the participants would have to respond to a stimulus.
- Central somatosensory conduction time was evaluated using the Nihon Kohden Neuropack M1 MEB-9200 EMG/EP/IOM system (A sophisticated measurement unit used for this type of research).
- Arm pain intensity was rated using a 0-10 numeric rating scale, with 0 indicating no pain and 10 indicating worst pain possible.
- Neck disability index (NDI) was used to determine how neck pain was impacting participants’ daily life.
Participants were randomly assigned to either the control or the study group. The study group received posture corrective exercises using a biofeedback device. This was performed for 8 weeks with 3 sessions each week, while the control received no exercises. Results for the study were collected at 4 and 8 weeks.
When the two groups were compared at the start of the experiment, there were no significant differences in the characteristics of the groups such as age, height, weight, sex, history of neck pain, and lifesyle. There was, however, a significant difference in the smoking statuses of participants between the groups.
At 4 weeks, both groups had seen a change in reaction time, arm pain, N13, N20 and CVA (All somatosensory evoked potentials in the brain) and the Neck Disability Index, but not central somatosensory conduction time compared to when they first started. At 8 weeks this difference was maintained, and the study group also saw a significant difference in central somatosensory conduction time while the control group did not.
The interesting results for us are the differences between the groups. At 4 weeks there were differences in N13, N20, CVA, arm pain, and NDI between the study and control group, but no meaningful differences in reaction time and central somatosensory conduction time. At the 8-week mark, there were significant improvements in the study group in all variables, including reaction time and central somatosensory conduction time, compared to the control group.
The results of this study demonstrate that 8 weeks of biofeedback posture corrective exercises can decrease both reaction time and central somatosensory conduction time in patients with forward head posture and cervical radiculopathy.
This is significant, and it is not the first study that has indicated improvements far beyond the 4-week mark that were not noted at this original time point. Kelly Holt’s seminal work on falls risk reduction in older adults under chiropractic care noted a peak at 12-weeks that was not present at 4-weeks [2]. This novel finding may give us some rationale to study the efficacy of chiropractic care or biofeedback over longer time periods.
Why Might BioFeedback Cause Such Improvements?
While certainly more research is required to confirm and explain the effect, there may be some logical explanations as to why biofeedback might reap such rewards. Reducing the tension placed on the spinal cord by correcting the abnormal posture may have lead to the decrease in central somatosensory conduction time. This decrease in conduction time, indicating improved conduction of messages being sent along the spine, may have had the positive impact on reaction time observed.
As with every study, there are limitations (which essentially give us the gift of considerations for future studies). In this case, the study was limited by the age of the included participants. This range was chosen as it has a high incidence of forward head posture due to extended work periods. At this point, the study has no follow up data and thus we know nothing about long term or lasting effects.
This would certainly be an interesting angle to explore. In the meantime, we have some pretty solid evidence that forward head posture is big news for somatosensory function and anything we can do, including the use of biofeedback devices and exercises following chiropractic care, is important.
References
- Mohamed AA, Jan Y-K, Raoof NA, Kattabei O, Moustafa I, Hosny H. Effect of Biofeedback Corrective Exercise on Reaction Time and Central Somatosensory Conduction Time in Patients With Forward Head Posture and Radiculopathy: A Randomized Controlled Study. Journal of Chiropractic Medicine. 2022
- Holt, Kelly R et al, “Effectiveness of Chiropractic Care to Improve Sensorimotor Function Associated With Falls Risk in Older People: A Randomized Controlled Trial,” Journal of Manipulative and Physiological Therapeutics.
