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A comprehensive analysis of muscle recruitment patterns during shoulder flexion: An electromyographic study
Wattanaprakornkul, Duangjai Halaki, Mark Boettcher, Craig Cathers, Ian Ginn, Karen A.
Wattanaprakornkul, Duangjai
Halaki, Mark
Boettcher, Craig
Cathers, Ian
Ginn, Karen A.
Abstract
Although flexion is a common component of the routine clinical assessment of the shoulder the muscle recruitment patterns during this movement are not clearly understood making valid interpretation of potential muscle dysfunction problematic. The purpose of this study was to comprehensively examine shoulder muscle activity during flexion in order to compare the activity levels and recruitment patterns of shoulder flexor, scapular lateral rotator and rotator cuff muscles. Electromyographic (EMG) data were recorded from 12 shoulder muscles sites in 15 volunteers. Flexion was performed in standing in the sagittal plane at no load, 20%, and 60% of each subject's maximum load. EMG data were normalized to maximum values obtained during maximum voluntary contractions. Results indicated that anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, upper, and lower trapezius were activated at similar moderate levels. However, subscapularis was activated at low levels and significantly lower than supraspinatus and infraspinatus. Similar activity patterns across time were demonstrated in the muscles that produce flexion torque, laterally rotate the scapula, as well as supraspinatus and infraspinatus, and did not change as flexion load increased. The onset of activity in supraspinatus and anterior deltoid occurred at the same time and prior to movement of the limb at all loads with infraspinatus activity also occurring prior to movement onset at the medium and high load conditions only. Posterior rotator cuff muscles appear to be counterbalancing anterior translational forces produced during flexion and it would appear that supraspinatus is one of the muscles that consistently “initiates” flexion. Clin. Anat. 24:619–626, 2011. © 2011 Wiley-Liss, Inc.
Keywords
shoulder, electromyography, flexion, rotator cuff, motor control
Date
2011
Type
Journal article
Journal
Clinical Anatomy
Book
Volume
24
Issue
5
Page Range
619-626
Article Number
ACU Department
School of Behavioural and Health Sciences
Faculty of Health Sciences
Faculty of Health Sciences
Relation URI
DOI
Source URL
Event URL
Open Access Status
License
File Access
Controlled