The electromyographic activity of thoracic paraspinal muscles identified as abnormal with palpation

Introduction

Early osteopathic research is often quoted to support the proposal of paraspinal muscle overactivity associated with intervertebral dysfunction, but these studies are dated and lack valid analysis.³ The aim of this study was to compare the EMG activity of deep muscles in the thoracic paravertebral gutter (PVG), detected as abnormal to palpation (AbPT) and reported as tender by the subject, with muscles underlying non-tender, normal to palpation (NT) sites.

Methods

Fine-wire, bi-polar intramuscular electrodes were inserted, under real-time ultrasonic guidance, into the deep paravertebral muscle mass underlying one AbPT and two NT sites (one segment above and below the AbPT site) in the thoracic PVG regions of 12 healthy subjects (mean age=25.42 years, range=22–43 years). EMG activity was recorded under the following conditions: resting prone, prone active trunk extension, application of pressure (300kPa) to adjacent spinous processes, resting seated, passive and active seated trunk rotation, and supporting 2kg weights in outstretched arms. EMG values were normalised to the mean peak amplitude at each site obtained under any of the conditions.

Results

There was a trend for increased normalised EMG activity at the AbPT site, relative to NT sites, with a significant difference between the AbPT and NT sites under the condition of resting seated (F_2,31=03.56, P=0.04), and medium and large effect sizes were calculated for many of the conditions. There was also a trend for a lower percentage change from baseline resting at the AbPT sites, relative to the NT sites, under the demands of other conditions. There were large variations in normalised EMG activity within and between individuals, and large standard deviations accompanied the means of EMG activity in all cases.

Conclusion

The findings of this study suggest that increased motor activity may be a contributing factor to tissue changes in the PVG detected with palpation, but caution must be used when interpreting these results due to the large variations and small sample size.

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