The Six Senses and Chiropractic Part 1: Proprioception

In days gone by, the strongest evidence surrounding chiropractic pertained only to lower back pain or the realms of musculoskeletal complaints. While that might be the definition that the uninformed still hold us to, it’s no longer solely what the evidence illustrates. We are now seeing increasing evidence that chiropractic care can change the structure and function of the brain, offer positive impacts well beyond the realm of musculoskeletal complaints and improve multiple aspects of quality of . In this series we will be shining a little light on how chiropractic can impact the six senses.

Before you go thinking the Australian Spinal Research Foundation has taken a dip into the metaphysical, the sixth sense we refer to in this series is proprioception – our sense of where we are in space. Proprioception is essential to balance and movement, and there are a number of chiropractic studies that offer strong indications that chiropractic care can improve this important sixth sense. Remarkably, it has only been in very recent history that this field of study has taken off.

Among the ground-breaking studies assisting us in understanding the mechanisms behind chiropractic was a 2011 study by prolific chiropractic researchers, Dr’s Heidi Haavik and Bernadette Murphy. The study, titled, “subclinical neck pain and the effects of cervical manipulation on elbow joint position sense,” took 25 subclinical neck pain patients and 18 control group participants and measured their joint position sense using an electrogoniometer [1].

For those with subclinical neck pain, a cervical adjustment intervention was carried out in the form of a HVLA thrust to the spine held in lateral flexion with slight rotation and slight extension. Notable results from the study included a significant improvement in the SCNP [subclinical neck pain] group’s absolute errors after cervical adjustments and an overall decrease in variable errors after the adjustments. Interestingly, the control group was significantly worse after the control intervention (which was a rest period between measures).

The conclusions reached by the researchers suggested that, “asymptomatic people with a history of SCNP have reduced elbow JPS [joint position sense] accuracy compared to those with no history of neck complaints. Furthermore, the results suggest that adjusting dysfunctional cervical segments in people with SCNP can improve their upper limb JPS accuracy [1].”

It was a very specific study, offering the dual benefits of confirming previous indications of impaired proprioception in neck pain patients, and indicating that adjusting dysfunctional cervical segments could improve upper limb proprioception. The study was indicative of more research that would emerge later, including a number of studies co-authored by Haavik showing the connection between chiropractic care and sensorimotor function or somatosensory evoked potential among other topics. But the road to such conclusions was not always straight-forward.

Earlier indications

In 2009, Learman et al examined trunk proprioception in subjects with chronic low back pain during symptom remission [2]. The study was limited to 35 (minus 2 non-completing) participants and was designed as a crossover trial. This meant that the trial participants were split into two groups. They either received a lumbar spinal manipulation or a sham procedure followed by a proprioception retest, and then one week later, they received the opposing option.

It was an interesting study design, and limited to only three interventions making it quite a short-term study. The first results weren’t encouraging, as both groups logged positive proprioception increases after the first adjustment – sham or otherwise. In fact, “Joint position sense tended to improve for both groups after spinal manipulation [1].” Following the study, it did not appear that “a single session of 1 to 4 thrusts of SMT produced and immediate or lasting impact on proprioception AE [absolute error] in subjects with chronic low back conditions who are pain free at the time of testing [2].”

It was a confounding study, as previous work had indicated a connection between spinal manipulation and improved proprioception. Among such work, a 1997 study had indicated a possible connection between spinal manipulation and proprioception in subjects with chronic neck pain, but the non-randomized nature of the study in combination with its small sample size left more to be desired in terms of evidence [3].

Three years later, a study published in the journal Spine highlighted differences in repositioning error in patients with low back pain, It was significantly higher than that of control subjects during flexion, leading researchers to comment on the implication that “some aspects of proprioception are lost in patients with low back pain [4].” An interesting finding of the study was that this error decreased in extension (possibly due to mechanoreceptor activity in the facet joints). Clearly, this work had implications for chiropractors and their patients.

During this time, there was significant evidence that showed impaired proprioception in patients with low back pain or chronic neck pain [5,6]. Still, chiropractic-specific data on this issue didn’t move forward in leaps and bounds for some years.

Chiropractic Care, Falls Risk and Proprioceptive Change

But then 2016 rolled around, and with it came the release of Dr Kelly Holt’s falls risk study. This time, the group studied was older adults (aged from 65 years). Proprioception was a key issue for this study, as joint position sense, choice stepping reaction time and postural stability were all measured as part of Holt’s research.

It should be noted that the chiropractors who took part in the study managed the participants as if they were normal patients, so there was no standardised treatment protocol or number of visits. In fact, the number of visits varied from 2 – 33 over the 12 weeks with an average of 21.9 visits. Still, some fascinating data emerged. Key findings of Holt’s study included [7]:

  • Significant improvements in ankle joint position sense error when compared with the control group
  • Significant improvements in choice stepping response time (showing increased sensorimotor function) at the 12-week mark in comparison with the control group.
  • Significant overall group effect of chiropractic care on susceptibility to the sound-induced flash illusion (which was designed to measure multisensory processing.)

Here, he uncovered something interesting. There were significant improvements noted at the 12-week mark in terms of increased sensorimotor function and choice stepping response time. This was not noted in the first 4 weeks.

This can lead us to speculate that perhaps the short nature of the Learman study limited their findings. It also highlights the importance of sticking with chiropractic care for 12 weeks or more, given this was when the increase in proprioception and sensorimotor function was noted.

We know the existence of data linking impaired proprioception with chronic neck and/or low back pain, just like we know that chiropractic care is recommended even by main-stream practitioners for low back pain. Thanks to Kelly Holt and colleagues, we are also beginning to see the wider impacts of chiropractic care on sensorimotor function beyond the low back pain issue, especially for the aging.

Though the research-related wish-list remains lengthy, it is encouraging to see these links between chiropractic care and proprioception.

Scoliosis

Nestled within the proprioception issue is an interesting recent discovery. There is emerging science indicating that adolescent idiopathic scoliosis could actually be a sensorimotor control problem. There are a number of factors contributing to the etiology of the condition, with genetic expression, environment and lifestyle factors impacting on asymmetrical bone growth along with neurophysiological and molecular factors [8].  However, Pialasse et al noted that, “a better understanding of the mechanisms leading to AIS [adolescent idiopathic scoliosis] inception and progression would help to improve the targeting of treatment [8].”

Pialasse and colleagues noted in their study of AIS and sensorimotor function that the vestibular system is worth considering as a potential risk factor in the onset of scoliosis. Furthermore, they noted “impairment of vestibular processing has already been established in patients with AIS at the level of cognitive integration. For instance, in the dark, after rotating their bodies along the vertical axis, patients with AIS underestimate the magnitude of body rotation more than do controls [8].” Their work goes on to explain the mechanisms by which the body believes it is upright, but shows that this can be compromised in small or significant amounts for people with AIS.

Their study assessed how the sensorimotor control mechanisms reacted during sensory alteration or transient sensory integration in order to measure balance control. What they found was fascinating.

“The present findings reveal that immediately following GVS [galvanic vestibular stimulation], compared with controls, the balance of control of adults with IS was impaired, because the RMS [root mean square] values of vertical forces and lateral horizontal displacement of C7 were greater than those of controls. This observation suggests that the sensorimotor control mechanisms of adults with IS work less effectively than those in controls. Therefore alteration in the mechanisms performing sensorimotor control may be related to the onset of scoliosis [8].”

This study has the potential to heap much importance on supporting the sensorimotor control in adolescence, as according to the authors “clinicians should consider that impairment of sensorimotor control is likely to be permanent in patients with scoliosis [8].” Such presentations shouldn’t be treated as transient states of delayed maturation.

Of course, further research is needed in order to bed down this theory. But the data so far should provoke thought: supporting proprioception and sensorimotor control in adolescent patients could reap a lifetime worth of benefits if we can get there before AIS develops.

So there you have it. Of course we have to be careful in what we confidently claim, and we haven’t seen science looking at AIS and chiropractic care as yet, but there are solid indications that we can have a positive impact on proprioception. This could indeed have a lifetime of benefits.

Up next in this series: The sense of touch: what the data says about chiropractic care and the neuropathies.

References

[1] Haavik H, Murphy B (2011), “Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense,” Journal Manipulative and Physiological Therapeutics, Vol. 34, Is. 2, 2011:88-97, DOI: https://doi.org/10.1016/j.jmpt.2010.12.009

[2] Learman K, Myers J, Lephart S, Sell T, Kerns J, and Cook C (2009), “Effects of Spinal Manipulation on Trunk Proprioception in Subjects with Chronic Low Back Pain During Symptom Remission,” JMPT, Vol 32, Number 2, pp. 118 – 126

[3] Rogers R (1997), “The effects of spinal manipulation on cervical kinesthesia in patients with chronic neck pain: a pilot study,” JMPT, 1997 Feb; 20(2):80-85

[4] Newcomer KL, Laskowski ER, Yu B, Johnson JC, & An K-N. Differences in repositioning error among patients with low back pain compared with control subjects. SPINE; 25(19): 2488-2493. 2000.

[5]  Brumagne SPT, Cordo PP, Lysens RMDP, Verschueren SP, Swinnen SP, (2000), “The role of paraspinal muscle spindles in lumbosacral position sense in individuals with and without low back pain,” J Spine, 25 (2000), pp. 989-994

[6] Paulus I, Brumagne S (2008), “Altered interpretation of neck proprioceptive signals in persons with subclinical recurrent neck pain,” J Rehabil Med, 40 (2008), pp. 426-432

[7] Holt K, Haavik H, Chi Lun Lee A, Murphy B and Elley C, (2016), “Effectiveness of Chiropractic Care to Improve Sensorimotor Function Associated with Falls Risk in Older People: A Randomized Controlled Trial,” JMPT, May 2016

[8] Pialasse J, Mercier P, Descarreaux M and Simoneau M (2016), “Sensorimotor control impairment in young adults with idiopathic scoliosis compared with healthy controls,” JMPT, September 2016, DOI: http://dx.doi.org/10.1016/j.jmpt.2016.06.001

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