Alterations of scapular kinematics and associated muscle activation specific to symptomatic dyskinesis type after conscious control

• Symptomatic subjects can actively maintain the scapula by conscious control.
• Conscious control of the scapula can be used to improve scapular external rotation during 3 selected exercises.
• Conscious control of the scapula can be used to improve MT, LT, and SA performance.
• Conscious control during side-lying external rotation can increase SA activity in patients with scapular dyskinesis.

BackgroundScapular orientation and movements can affect the function of the shoulder. However, evidence is limited on whether symptomatic subjects can actively maintain the scapula in a neutral position through conscious control.ObjectiveTo investigate whether symptomatic subjects with scapular dyskinesis can achieve optimal scapular movements and associated muscle activities through conscious control.DesignA cross-sectional study.MethodsSixty subjects with scapular dyskinesis (16 inferior angle pattern I, 16 medial border pattern II, and 28 mixed pattern) performed 3 selected exercises (arm elevation, side-lying elevation, and side-lying external rotation) with and without conscious control. Three-dimensional electromagnetic motion and electromyography were used to record the scapular kinematics and muscle activation during the exercises.ResultsFor scapular kinematics, significant increases in scapular external rotation (4.6 ± 3.2°, p < 0.0125) were found with conscious control during arm elevation and side-lying elevation in three groups. Significant increases in activation of the middle and lower trapezius (MT: 4.9 ± 2.4% MVIC; LT: 10.2 ± 6.8% MVIC, p < 0.0 25) were found with conscious control in 3 exercises among the 3 dyskinesis groups. Increased serratus anterior activation (SA: 11.2 ± 4.8% MVIC, p < 0.0 25) was found in the concentric phase of side-lying external rotation in the pattern I and I + II groups.ConclusionConscious control of the scapula can alter scapular orientation and MT, LT, and SA activation during 3 selected exercises in subjects with symptomatic dyskinesis. Specifically, conscious control during side-lying external rotation can be applied to increase SA activity in pattern I and I + II dyskinesis.