The effect of cervical spine manipulation on grip strength and muscle activity in asymptomatic participants with cervical spine dysfunction

Abstract

Objective: The effects of spinal manipulation are well documented, however there is a gap in the current literature regarding the neurophysiological mechanisms responsible for these effects. Further evidence is required to reveal the specific neurophysiological mechanisms of spinal manipulative therapy and its effect on muscle activity. The objectives of this study were to investigate the short-term effects of a single cervical spine manipulation on grip strength and muscle activity of the forearm flexors and extensors in an asymptomatic sample when compared to a control. Methods: A randomised, controlled, pre-test, post-test, repeated measures design allowed for 46 participants, aged 18-35 years old, with joint dysfunction at C7 to be allocated to either a cervical spine manipulation or a control group. Force output and muscle activity of the forearm flexors and extensors were measured before and immediately after the intervention and again at 5, 10 and 15-minutes. IBM SPSS was used to analyse the data with significance set at (p=0.05). Repeated measures ANOVA testing and Post hoc contrast studies were used to determine significance within, and between, groups. Results: In the treatment group there was a statistically significant change in muscle activity over time in the Extensor carpi radialis (p=0,013) and Extensor digitorum (p=0,021). Similarly, force output increased within the treatment group over time (p=0,012). A statistically significant beneficial treatment effect was identified between the groups in the Extensor carpi radialis (p=0,001) and Flexor digitorum superficialis (p=0,019) muscles only. Conclusion: Though statistical significance was not detected in all muscle groups, this study showed a trend of a treatment effect following cervical spine manipulation (C7) with most values lying just outside the parameters set for significance. Specific muscles of the forearm were affected more than others. Future studies are required with a larger sample to validate the trends observed in this study.