Spinal manipulation causes variable spine kinematic and trunk muscle electromyographic responses

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Abstract

Study design. Analytic cohort with a convenience sample in a research clinic.

Objectives. To determine the influence of a spinal manipulation on trunk kinematics and associated trunk myoelectric activity.

Summary of background. While the mechanism of spinal manipulation is unknown, it has been theorized to influence spinal range of motion and trunk muscle activity.

Methods. Trunk kinematics were measured in low back pain patients (n=14) during simple range of motion tasks in three planes, while trunk muscle electromyogram signals were recorded bilaterally from paraspinal and abdominal musculature. Kinematics and electromyogram signals were assessed pre–post manipulation. Electromyogram activity was also assessed pre–post manipulation during quiet stance.

Results. While no consistent kinematic or electromyographic changes occurred following manipulation across the population, individual changes were observed. The largest changes (>6°) in range of motion occurred in the sagittal plane of three patients experiencing the greatest amount of pain. During quiet stance 17 muscles across all subjects exhibited changes in muscle activity following manipulation. Sixteen of those changes were decreases in muscle amplitude.

Conclusions. This study offers some preliminary data on the short-term effects of manipulation on lumbar range of motion and dynamic electromyogram. The findings suggest that the response to manipulation is variable and dependent on the individual, with no change in some to the largest changes seen in the more pained patients.
Relevance

Basic science investigations into the mechanisms and biomechanical influences of spinal manipulation are few. This study attempts to address issues of measureable functional change with manipulative therapy.

Introduction

Spinal manipulation (SM) has been theorized to influence biomechanical function of the spine and its associated soft tissues, specifically modulation of muscle activity and increased joint range of motion. The intent of this study was to evaluate these notions by documenting the short-term influence of a spinal manipulation on lumbar spine kinematics and associated trunk muscle activity.

Previous work investigating the effects of SM on spine biomechanics has documented reflexive changes, as seen in the electromyogram (EMG) of the trunk and limb muscles following a manipulative thrust [1]. In the same study, a single case demonstrated a reduction in muscle activity immediately following manipulation during a static task. In addition, Shambaugh et al. [2] reported a decrease in EMG amplitude of the erector spinae musculature following manipulation during a prone lying task. This short-term reduction in paraspinal muscle activity, during quiet standing, has also been documented over a period of one week [3]. Manipulation has also been associated with a decrease in amplitude of the H-reflex of the tibial nerve following sacroiliac manipulation [4]. All of these studies have focussed on EMG changes during static tasks. Although it is a common claim that manipulation improves range of motion, evidence pertaining to the low back is scarce. There is some evidence, however, on the influence of a cervical manipulation on neck range of motion. For example, Nansel et al. [5] demonstrated increases in cervical lateral bending range of motion immediately following a manipulation in subjects exhibiting pain and in an asymptomatic population.

It was the purpose of this study to assess lumbar muscle activation and range of motion changes resulting from SM during dynamic movement trials.

Section snippets

Subjects

Patients were recruited from the UW-CMCC Chiropractic Research Clinic. Fourteen subjects exhibiting non-specific low back pain participated in the main study investigating dynamic tasks. A subset of seven participated in quiet standing trials. Five additional subjects with non-specific low back pain were recruited to participate solely in that part of the study investigating the effect of a manipulation on EMG activity during quiet stance (thus, the 19 subjects formed two groups; one consisting

Results

The global results of the immediate effect of SM on the lumbar spine peak range of motion and on muscle activity will be presented first followed by a case study.

Case Study #1

A 28 year old male (height=172 cm, weight=69 kg), with a three year history of low back pain was in the midst of an acute episode of pain (scoring 35/50 on the Oswestry Low Back Pain Disability Index). The patient experienced dispersed pain throughout the lumbar region as well as referred pain to the right anterior abdominal wall below the anterior superior iliac spine –corresponding to the right internal oblique. For this reason, an additional pair of electrodes was affixed to the skin over

Discussion

Changes in spinal range of motion following manipulation were small and tended to be increases rather than decreases, if they did occur at all. The largest changes were increases in range of motion occurring in patients who exhibited the greatest amount of pain and the smallest initial range of motion. Subjects who showed changes in their range of motion following manipulation maintained those changes for at least 20 min. Some may consider this a window of increased range of motion which may

Summary and conclusions

In a few patients kinematic changes due to SM were observed although there was no systematic increase or decrease – they appeared to be dependent on the individual. The greatest changes in kinematics and muscle activity were seen when dysfunction and pain were the largest. Observed myoelectric changes in a muscle some distance from the spine, suggests manipulation can affect muscles other than those paraspinal. Future work needs to address clinical significance of these biomechanical changes

Acknowledgements

The author gratefully acknowledge the financial support of the Natural Sciences and Engineering Research Council (NSERC) together with Dr. Mohsen Kazemi and Dr. Rhonda Kirkwood for clinical consultation with patients.

References (8)

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