A Comparison of EMG Signals from Surface and Fine-Wire Electrodes During Shoulder Abduction

Bala S Rajaratnam

doi:10.4172/2329-9096.1000206

Abstract

Electromyography quantifies the action of muscles and the data provides an understanding of how coordination occurs during an action. This concurrent comparison research study evaluated electromyography signals from surface and fine-wire electrodes placed simultaneously on selected shoulder muscles. A stand-alone data logger collected electromyography signals from both types of electrodes placed on and within the teres major, supraspinatus, infraspinatus and posterior deltoid muscles as 30 healthy adult subjects performed overhead shoulder abduction. There were poor correlation in the timing of onset and peak magnitudes between fine-wire and surface electrodes reading of teres major, infraspinatus and supraspinatus (onset r=-0.01-0.07; p>0.05, peak r=0.05-0.10; p>0.05). Readings from surface electrodes placed on the posterior deltoid was strongly correlated with its fine-wire temporal values (onset r=0.94, peak r=0.90; p<0.00). Fine-wire electrodes are able to record time sensitive information of how the rotator cuff muscles controls glenohumeral motion during overhead shoulder abduction. The findings are important when deciding to use electromyography to study muscle co-ordination at the shoulder for orthopaedic and neurological rehabilitation.

Highlights

By studying the dynamic characteristics of muscle, one is able to understand the regulation of motor control during motion
EMG analysis of neuromotor coordination indicated that recurrent dislocation of the shoulder after surgical stabilization could be due to altered neuromotor coordination of the glenohumeral muscles [5]
Signals from Surface electromyography electrodes (sEMG) placed on deep muscles were quite different from fine-wire electromyography signals of the same muscles [2,7,8,9]. sEMG recorded two times more cross talk compared to reading from fEMG electrodes of the muscle. fEMG electrodes picked up less surrounding muscle activities compared to surface electrodes and its signals were more repeatable on the same-day compared with sEMG [9,10,11,12]

Summary

Introduction

By studying the dynamic characteristics of muscle, one is able to understand the regulation of motor control during motion. Electromyography (EMG) identified the timing and amplitude of motor unit action potential of muscles during performance of functional tasks or neuromotor coordination; features that other movement analysis devices are unable to quantify [1,2]. The decision to use surface or fine-wire electrodes depends on the properties of the muscles being studies. Surface electromyography electrodes (sEMG) have a large pick-up area, but accurately captured the activity of superficial muscles that are less than 1.8 cm deep [6]. SEMG recorded two times more cross talk compared to reading from fEMG electrodes of the muscle. FEMG electrodes picked up less surrounding muscle activities compared to surface electrodes and its signals were more repeatable on the same-day compared with sEMG [9,10,11,12] Signals from sEMG placed on deep muscles were quite different from fine-wire electromyography (fEMG) signals of the same muscles [2,7,8,9]. sEMG recorded two times more cross talk compared to reading from fEMG electrodes of the muscle. fEMG electrodes picked up less surrounding muscle activities compared to surface electrodes and its signals were more repeatable on the same-day compared with sEMG [9,10,11,12]

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Discussion

Conclusion