The effect of cervical spine manipulation compared to muscle energy technique on neck muscle activity and range of motion in asymptomatic participants

Abstract

Background: Clinical evidence supports the use of spinal manipulative therapy (SMT) and muscle energy technique (MET) for the treatment of cervical spine dysfunctions. However, the physiologic mechanism behind their effectiveness is not well understood. Joint dysfunctions are associated with hypertonicity of segmentally related muscles and can occur in both symptomatic and asymptomatic individuals. Neck pain (NP) has been associated with cervical muscle dysfunction, due to the presence of altered muscle activity and impaired kinematics, demonstrated in NP patients. This includes the upper trapezius and posterior cervical muscles, whose dysfunction can be a source of NP. Spinal manipulative therapy and MET are mechanical interventions, that when applied to joint dysfunctions, produce neurophysiological changes, specifically the modulation of muscle activity and improved range of motion (ROM). However, the demonstration and comparison of the neurophysiological effects of SMT and MET in the neck, and its related musculature, are unknown. Aim: The aim is to determine the effect of cervical spine manipulation compared to MET on neck muscle activity and range of motion in asymptomatic participants. Method: This is a quasi-experimental study utilising a pre-test, post-test design, which employed 50 asymptomatic participants aged between 18 – 35 years of both genders and all races. The participants were randomly allocated into one of two treatment groups. Group 1 received cervical spine manipulation (CSM) and Group 2 received MET. Before and after the respective interventions, resting upper trapezius and posterior cervical electromyographic muscle activity and the cervical spine range of motion (CROM) (lateral flexion and extension) were measured. The IBM SPSS version 24 was used to analyse the data. The intra-group changes were compared pre- and post-intervention using paired Wilcoxon signed ranks tests. Median changes between pre- and post- were compared between the two treatment groups using Mann-Whitney U tests. A p value < 0.05 was considered as statistically significant. Results: None of the demographic or background variables differed significantly between the two groups. Both treatments had an effect, although not all significant, involving mostly reductions in resting electromyographic muscle activity and improvements in CROM. This was significant for the right posterior cervical muscles in the SMT group (p = 0.012) and for ROM in both groups (p < 0.001). No evidence of a difference in treatment effect was found. Conclusion: The results of this study suggest that SMT and MET mostly decrease resting neck muscle activity and improve CROM. Muscle energy technique may possibly be equally as effective as CSM. Concurrent changes in both outcomes suggest that more than one physiologic mechanism may likely explain these effects.