The immediate effects of thoracic spine grade III mobilisation on the muscle activity of the middle and lower trapezius muscle

Abstract

Background: Thoracic spine dysfunction often presents with regional hypomobility which is often caused by abnormal muscle activity in the overlying area. Such as the trapezius muscle. Joint dysfunction is often treated by manual therapies such as joint mobilisation. Previous studies have established that joint mobilisation improves joint mobility, achieves hypoalgesia, improves stability, range of motion and proprioception. Although documented in the literature, the direct benefits of joint mobilisation on muscle activity are not well understood. Therefore, an investigation into the effects of mobilisation on muscle activity was explored. Aim: This study aim was to determine the immediate effects of thoracic spine grade III mobilisation on the muscle activity of the middle and lower trapezius muscles. Methods: This was a quantitative, experimental, study with a pre-test post-test design. Surface electromyography was used to measure the muscle activity of the middle and lower trapezius muscle. A sample size of 48 asymptomatic participants were recruited and randomly divided into the intervention or control group. The intervention group received thoracic grade III mobilisation and the control group remained prone between the pre-test and post-test readings. Within group comparisons was achieved using paired T-tests. Within group and between group comparisons of the change between pre and post intervention was achieved using repeated ANOVA testing. A p-value below 0.05 was considered significant. Results: Spinal mobilisation had no effect on muscle activity. Despite the lack of statistical evidence, there was a positive trend in the effects of thoracic spine mobilisation with a borderline treatment effect in the left middle trapezius muscle (p = 0.063). There was an overall decrease in muscle activity in the intervention group. Conclusion: The results showed that mobilisation did not produce a noteworthy change in muscle activity of middle and lower trapezius muscles between the intervention and control groups and the null hypothesis was not rejected.