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

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.

Electromyographic Characteristics of a Single Motion Shoulder Exercise: A Pilot Study Investigating a Novel Shoulder Exercise

“…First, the value of using surface EMG electrodes for the measurement of shoulder muscles has been questioned. 18,19 However, the authors feel that any error introduced by using surface electrodes would be equal for each exercise trial since the data were case-controlled.…”

Differences in muscle contraction onset as determined by ultrasound and electromyography

“…Chimera et al found no electrode differences in onset timings within the plantarflexors during walking . In contrast, Rajaratnam et al found poor relationships in contraction onset between electrode types in smaller deep muscles (infraspinatus, supraspinatus, and teres major; r = ‐0.01–0.07) and excellent relationships for larger muscles (posterior deltoid; r = 0.94) during shoulder abduction. Possibly due to improper instrumentation in that study, cross‐talk from the larger posterior deltoid likely obscured the sEMG recording of the smaller muscles, causing false onsets.…”

“…1,2,4 Reasonable correlations between sEMG and fwEMG were found in the lower limb during walking, 16 while inconsistent correlations were found in shoulder muscles during abduction. 17 The fwEMG and ultrasound onset were inconsistent with each other, 11,13,18 while others have reported moderate relationships between sEMG and ultrasound onset. 14 Differences in muscles, contraction tasks, and experimental designs (e.g., number of repetitions, averaging methods) may explain specific levels of agreement between studies; however, during a re-analysis of published EMG-and ultrasound-derived contraction onset studies, Dieterich et al 18 noted a surprisingly high number of trials within each study (17-72%) where ultrasound onset was detected before electrical activation.…”

“…Despite measuring different aspects of muscle contraction, direct comparisons of onset times between modalities are common in the clinic literature . Reasonable correlations between sEMG and fwEMG were found in the lower limb during walking, while inconsistent correlations were found in shoulder muscles during abduction . The fwEMG and ultrasound onset were inconsistent with each other, while others have reported moderate relationships between sEMG and ultrasound onset .…”

Analysis Of A Low-Cost Sensor Towards An Emg-Based Robotic Exoskeleton Controller

“…Additionally, the design of the electrodes, the distance between them, and the placement and the orientation of them along the muscle affect signal fidelity. Furthermore, the quality of the contact between the electrodes and the skin, the wire length to the amplifier, the characteristics between the electrodes [4], the amplifier unit, and the signal processing methods are also important. There are many factors which can influence the EMG signal on the subject side as well, such as the conditions of the muscles.…”