Effects of Lumbar Stabilization on Scapular Muscle Activity, Activation Onset Time, and Kinematics in Individuals with Scapular Dyskinesis
(Sumarttra Sungkue, Prasert Sakulsriprasert, Mantana Vongsirinavarat, Nalut Utsahachant, Mark P. Jensen)

This study aimed to investigate the effects of lumbar stabilization on muscle activity, muscle onset time, and scapular kinematics in individuals with scapular dyskinesis. Fourteen participants with scapular dyskinesis were recruited. Scapular muscle activity and activation onset time were measured by electromyography (EMG), and scapular upward rotation was measured by two-dimensional (2-D) Kinovia software, under two conditions: with and without abdominal bracing. There was a significant increase in the activity of the serratus anterior, middle trapezius, and inferior trapezius muscles between the conditions (p < 0.001, p = 0.045, and p < 0.001, respectively). During abdominal bracing, the activation onset time of the serratus anterior and lower trapezius was noticeably shorter (p = 0.041 and p = 0.011, respectively). Scapular upward rotation at 30°, 60°, 90°, and 120° of shoulder abduction was significantly greater (p = 0.027, p = 0.003, p = 0.003, and p = 0.030, respectively). Increased scapular muscle activation, early activation onset time, and increased scapular upward rotation were also noted. These changes have an impact on the scapulohumeral rhythm.