Motion analysis study of a scapular orientation exercise and subjects' ability to learn the exercise

Exercises to retrain the orientation of the scapula are often used by physiotherapists to optimise shoulder girdle function. The movements and muscle activity required to assume this position have not yet been quantified. Further, patients often find this a difficult exercise to learn accurately, with no data being available on the accuracy of repeated performance. The primary objective of this study was to quantify the movements occurring during a commonly used scapular orientation exercise. The secondary objective was to describe the ability of subjects to learn this position after a brief period of instruction. A group of normal subjects (13 subjects; mean age 32, SD=9) were taught the scapular orientation exercise. Measurement of the position and muscle actions were made with a motion analysis system and surface electromyography. Further comparison was made of the accuracy of repeated trials. The most consistent movements were upward (mean=4 degrees, SEM=0.9 degrees) and posterior rotation (mean=4 degrees, SEM=1.6 degrees). All parts of the trapezius muscle demonstrated significant activity in maintaining the position while latissimus dorsi did not. Repeated trials showed that subjects were able to accurately repeat the movement without guidance. The key movements of, and immediate efficacy of a teaching approach for, scapular orientation have been established.