A comparative study of shoulder muscle strength, sense of proprioception and internal/external rotation flexibility between adolescent athletes with and without scapular asymmetry

Introduction
Scapular asymmetry may affect the biomechanics of the shoulder girdle joints and muscles by changing the contraction angles of the muscles. The purpose of this prospective cohort, matched-controlled study was to compare shoulder muscle strength, proprioception sense and internal/external rotation flexibility between adolescent athletes with and without scapular asymmetry.



Material and methods
Nineteen athletes of tennis, fencing, shooting, archery, gymnastics, and badminton branches with left side (non-dominant) scapular asymmetry were included in the study as asymmetry group. Nineteen athletes who have similar gender, sports branch, professional experience, physical characteristics with asymmetry group were included in the study as the control group. Scapular asymmetry was measured using a tape measure with the Lateral Scapular Slide Test. Shoulder horizontal abduction/adduction isokinetic muscle strength and shoulder abduction/adduction isometric muscle strength was tested by an isokinetic dynamometer. The proprioception sense of the glenohumeral joint was evaluated with a digital inclinometer, and the flexibility of the internal and external rotation of the shoulder was evaluated by the flexibility test.



Results
There was not any significant difference between the groups in isokinetic muscle strength, isometric muscle strength, and proprioception sense of shoulder (p>0.05). Shoulder internal rotation flexibility of both dominant and non-dominant sides was higher in the asymmetry group than the control group (p<0.05).



Conclusions
It was determined that the flexibility of shoulder internal rotation in adolescent athletes with scapular asymmetry was higher than those without asymmetry.