A new study published in the Journal of the Canadian Chiropractic Association has presented some interesting considerations for both healthy, young patients and researchers. It looked at the topic of postural influences on neck proprioception and head/neck stabilisation and found “a significant effect of both posture and vision for both vertical and horizontal head movements during the head-still task [1].”
Proprioception, or the sense of where we are in space, is a sixth sense of sorts. Generally speaking, it is known to “play a major role in the control of posture and gait in humans,” and “when neuromuscular function at the neck is impaired either by pathology, trauma or by experimental manipulations in healthy subjects (such as neck fatigue) balance and movement control have been shown to decrease [2, in 1].”
It’s a topic that has been examined by chiropractic researchers such as Dr Kelly Holt and Dr Heidi Haavik when examining the effects of chiropractic care on joint position sense or in falls risk. The connections between improved proprioception and chiropractic care are documented, especially when it involves subclinical neck pain, low back pain or advanced age [3,4,5].
So what happens when the patients are young and asymptomatic?
This study took in a sample of 12 healthy college students, 4 males and 8 females aged between 20 and 31. Exclusion criteria ensured all subjects were free from vestibular, neurological or injury-related factors that might truncate the results. They were put through a 60-minute laboratory session during which they completed two tasks, both of which involved four postural conditions (sitting, standing, kneeling, and sitting with stabilization):
- The head repositioning task saw participants “fitted with an adjustable bicycle helmet with laser pointer fixed on top, while wearing a blindfold. The helmet was placed on the head such that the laser pointer was facing directly forward…Blindfolded subjects with eyes closed, wearing the laser mounted helmet were placed 2.6 meters from the projection screen which was adjustable in height to accommodate all postures. Participants were instructed to: a) memorize their neutral head position, ‘put your head into what you think is a straight ahead position’ and hold for two seconds; b) perform a near maximal head rotation to the left (or right) for approximately two seconds; and c) to relocate the head to the initial neutral reference head position with maximum precision but without speed instruction and to hold the position for 2 seconds (to allow experimenters to register the position on the screen).
- The head still task used the same postures and equipment. This time, “While located 2.6 meters in front of the projection screen, participants were instructed to maintain the laser dot on a colored target circle that was 1.91 cm in diameter for 30 seconds. Two trials were performed in each of the four postures, one trial with eyes open and no mask, the other with eyes closed wearing the mask.”
- Video analysis was used to determine laser dot positioning, and no feedback was given to participants.
The results indicate postural effects on neck proprioception, an issue the authors flag as a consideration for researchers. While no significant effects were found in the head-repositioning task, the effects in the head-still task were notable. The authors remarked that:
“The main findings of this study were that body posture did not influence head repositioning accuracy (either with head rotation to the right or to the left) but did influence head stabilisation (head still) performance. There was a significant effect of both body posture and vision on both horizontal (x) and vertical (y) head movements during the head stabilization task with the two-seated conditions yielding the least amount of head movement. “
They said that:
“We hypothesized that joint position error during the head repositioning task would be reduced when segments other than the neck could contribute to the perception of the orientation of the head in space. We failed to find evidence to support this hypothesis. Rather, it appears that the participants were equally successful at repositioning their heads in space regardless of the number of joints allowed to contribute towards their performance. We take this to mean that for our healthy participants’ head repositioning task to be effective, only the cervical spine need be operational. Adding further degrees of segmental freedom is not required, nor helpful in the task of head repositioning accuracy. Our results call into question the hypothesis of a proprioceptive chain – at least with respect to this task and in a healthy population
What does this mean in clinical practice? The researchers explained that:
“For healthy young adults, clinicians and researchers need to be concerned with postural influences on tasks that involve head/cervical spine stabilization. Contrary to our hypothesis, we provide evidence that during the head still task, more joint degrees of freedom led to increased movement variability of the head. Clinicians can be confident that performing head repositioning accuracy tasks in a variety of postures will likely not change their results for healthy, young asymptomatic subjects. “
It would certainly be interesting to repeat the experiment in whiplash patients or a neck pain population (which already carries a risk of lowered proprioception). In the mean time, the original paper is well worth a read as it contains a lengthy discussion on the muscle-spindle inputs and other connections within the vestibular, visual and sensory systems and how they may impact on proprioception.
You can find the original article at the open-access journal (link below [1]).
REFERENCES:
- Smith DL, Haug MJ, Walsh MS (2019), “the effect of posture on neck proprioception and head/neck stabilization in asymptomatic participants,” Journal of the Canadian Chiropractic Association, https://www.chiropractic.ca/wp-content/uploads/2019/08/114494-1_Chiro_63_2e_Smith.pdf retrieved 24 October
- Pinsault N, Fleury A, Virone G, Bouvier B, Vaillant J, Vuillerme N. Test-retest reliability of cervicocephalic relocation test to neutral head position. Physiother Theory Pract. 2008;24(5):380-391.
- Haavik H, Murphy B (2011), “Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense,”Journal Manipulative and Physiological Therapeutics, 34, Is. 2, 2011:88-97, DOI: https://doi.org/10.1016/j.jmpt.2010.12.009
- 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
- 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
- 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.
