The effects of an upper cervico-thoracic segment manipulation on posture and muscle activity in participants with forward head and round-shouldered posture
Authors:   , Petzer Matthew 
Published: August 2023

Background: Postural dysfunction in the cervico-thoracic spine often leads to segmental restrictions and hypomobility, and this is often caused by biomechanical alterations due to postural changes and over activity of skeletal muscles in that region. These muscles include the pectoralis and trapezius muscles. Postural dysfunction and joint restrictions are often treated by manual therapies, such as spinal manipulation. Previous studies have established that joint manipulation reduces postural dysfunction and improves joint mobility, which could be explained by a combination of neurophysiological,and biomechanical effects.In literature, the immediate benefitsof acervico-thoracicmanipulation on muscleactivityandposture are not well understood and, therefore, an investigation into the immediate effects of manipulation on muscle activity and posture was implemented in this study. Aim: This study aimed to observe the immediate effect of an uppercervico-thoracic segment manipulation on posture and muscle activity in participants with forward head and round-shouldered posture. Methods: This study was a quantitative, observational study with a pre-test posttest design. Surface electromyography was used to measure the muscle activity of the pectoralis major, upper and middle trapezius muscles prior to and after the cervico-thoracic intervention. A sample size of 40 asymptomatic participants were recruited to participate. The participants were randomly divided into two groups: group A, which was the control group, and group B, which was the intervention group. The intervention group received a cervico-thoracic manipulation, but the control group received no intervention and remained prone for 3 minutes between the pre-test and post-test readings. The within-group comparisons of pre- and postmuscleactivity were achieved usingpairedT-tests. Within groupandbetween group comparisonsof the change between pre- andpost-intervention wereachieved using repeated ANOVA testing. A p-value below 0.05 was statistically significant. IBM Statistical Package for Social Sciences (SPSS) version 26 software was used to process the data. Results: There was no statistically significant treatment effect of cervico-thoracic spinal manipulation in the effects on muscle activity. Although there was not a statistically significant change in muscle activity, there was a positive change in pectoralis major compared to the upper or middle trapezius. The upper and middle trapezius muscles decrease activity followed an evident trend between the participants who received the intervention compared to the control group. Postural results were not statistically significant but positive correlations to treatment were found. The craniovertebral angle was seen to decrease at a higher rate compared to the control group. Additionally, the study provided evidence of a treatment effect on the acromiovertebral angle, decreasing overall in severity. Conclusion: The results of this study do not provide conclusive evidence that the intervention has any immediate statistical effect on the three muscle activity measurements outcomes observed. In terms of the Posture Pro Analysis System measurements, changes (decrease in angles) between the pre- and postintervention were mostly significant in both groups, but statistically there was no difference between the control and intervention groups. Posture Pro ratings did not provide evidence of changes in categories within the groups. Therefore, the null hypothesis was retained.