The effect of cervical spine manipulation on elbow proprioception, electrical activity of the triceps and biceps muscles and balance
Authors:   , McKay Hannah Lenka 
Published: October 2021

Objectives The purpose of this study was to determine the effect of cervical spine manipulation (CSM) on joint position sense (JPS) of the elbow; electrical (muscular) activity of the biceps and triceps brachii muscles and balance. Background Balance is a complex process requiring constant communication between the visual, the vestibular and the somatosensory (nervous) systems. JPS and electrical activity of muscles play an important role in maintaining balance. Many of the tracts relaying information regarding JPS, electrical activity and balance pass through the cervical spine. It is thought that cervical spine fixations have a negative effect on the surrounding neurology and thus affect somatosensory integration. Therefore, correction of cervical spine fixations with CSM may improve and restore normal function, including, but not limited to, elbow JPS, electrical activity of the biceps and triceps brachii muscles and balance. Methods Institutional Research Ethics Committee (IREC) approval of the study was obtained (IREC reference number: REC 115/16). A quantitative, descriptive, pre-test post-test randomised control trial investigation design was utilised. A pilot study was performed to validate the experimental procedures. Potential participants were assessed through a telephonic interview, a case history and a physical examination, to screen them against the inclusion criteria. Eighty-one participants between the ages of 18-35 years were randomly allocated to either the control (n = 20) or the intervention group (n = 61). The intervention group was further stratified into three subgroups, namely upper cervical spine fixations only (C0-C3); lower cervical spine fixations only (C4-C7) and both upper and lower cervical spine fixations. Each participant completed two pre-tests for static balance (eyes open and closed) and dynamic balance (eyes open and closed) [Biosway Biopac balance system]; one pre-test for electrical activity of biceps and triceps brachii muscles at rest and then during an active movement; and one pre-test of the ipsilateral elbow for JPS [Biopac AcqKnowledge sEMG machine and goniometer]. All tests were performed on the dominant arm. The intervention group then received CSM to correct the fixated segments. The control group underwent a 20 second rest period instead of the CSM. The electrical activity of the biceps and triceps brachii muscles was recorded during the intervention period. The pre-tests were then repeated as post-tests immediately following the intervention. Analysis was by paired sample t-tests (pre and post outcomes for intra-analysis). Independent t-tests were conducted to determine mean differences between the control group and intervention group. An ANOVA test was conducted for mean differences from pre- and post-intervention readings between the control group and the three intervention subgroups. If the null-hypothesis was rejected, then post hoc tests were conducted to detect where the differences lay. A p- value < 0.05 was considered statistically significant. The effect size (Cohen’s d), was also used to determine the magnitude of the effect of interest. Results There was no statistically significant improvement in elbow JPS immediately following CSM. The combined intervention group showed a statistically significant increase in the electrical activity of biceps (p < 0.001) and triceps brachii (p = 0.004) muscles during the CSM. The group that received upper CSM only had the greatest increase during CSM in both muscles (p = 0.04 for biceps and p = 0.024 for triceps. This group also had a sustained increased electrical activity that was statistically significance for a 10% level of significance (p = 0.09), during the rest period. There was a statistically significant improvement in dynamic balance for the combined intervention group (p = 0.012). Of the subgroups, the lower CSM only group had the greatest improvement in dynamic balance (p = 0.035) followed by the upper CSM only group (p = 0.074, significant for a 10% level of significance). Comparison of the four groups indicated two trends in the outcomes. The first trend was that the upper CSM only group had the greatest effect size for elbow JPS improvement and increased electrical activity for the biceps and triceps brachii muscles during the intervention and rest period, as well as a statistically significant difference in dynamic balance at a 10% confidence interval (p = 0.074). The second trend was in the lower CSM only group, which had the greatest effect size in decreasing electrical activity during the active movement as well as the greatest statistically significant improvement in dynamic balance (p = 0.035). Conclusion This preliminary study indicates that there is no immediate improvement in elbow JPS following CSM as a once off intervention. CSM has an immediate effect on increasing electrical activity of the biceps and triceps brachii muscles during the CSM. CSM also improves dynamic balance. Upper CSM has the greatest effect on electrical activity during the CSM and rest period. Lower CSM has the greatest effect in improving dynamic balance.