Muscular activation patterns in swimmers with asymptomatic shoulder joint instability

Abstract

Purpose. The aim of this study was to investigate the (electromyographic) EMG patterns of the shoulder muscles in asymptomatic swimmers with AGI -atraumatic glenohumeral instability. AGI, one of the most common shoulder disorders in athletes who perform overhead activities, occurs especially among swimmers. AGI usually provokes shoulder pain and secondary impingement syndrome, which might alter glenohumeral and scapular kinematics and change the activity of the shoulder muscles. Alternatively, pain or functional activities might affect EMG patterns in individuals with AGI. Methods. Eight swimmers with AGI and eight healthy swimmers took part in this cross-sectional study. Bilateral and simultaneous shoulder elevations in the scapular plane toward three different target distances were investigated, and the shoulder kinematics and EMG activities of the glenohumeral and scapulothoracic muscles were also collected. Results. No differences in the EMG patterns were found between swimmers with and without AGI in terms of the rate of EMG rise and magnitude. Conclusions. Shoulder instability does not necessarily affect the modulation of the shoulder muscles in swimmers with AGI. Others factors such as laxity in the capsular structures and ligaments may be one of the primary reasons for pain and instability in these athletes.

Relationship between anthropometric and electromyographic variables of the scapular muscles

“…in this context, there are no studies that evaluate the influence of adipose tissue accumulation on the onset latency, especially of muscles that are part of the axial skeleton. The variation of latency is an important indicator of neuromuscular control, as it allows estimation of the recruitment order of the muscles that stabilize and mobilize a joint [16][17][18]. in this sense, it is important to understand the relationship between skinfolds and the onset latency of the scapular muscles, as if there is a relationship, this would be a determining factor when evaluating, analysing, and interpreting the surface EMG record.…”