Background: Scapular dyskinesis is characterized by altered scapular position and motion. Specifically, excess activation of the Upper trapezius (UT) combined with decreased Lower trapezius (LT) and Serratus anterior (SA) have been observed. The Standard push-up plus exercise (SPP) is considered as a therapeutic exercise for increasing SA activity and maintaining the scapular kinematics. In addition, Using the Sling surface can lead to higher muscle activity. However, the advantage of an unstable surface has been uncertatin. Objects: To compare the activation of the UT, LT, and lower serratus anterior (LSA) muscles during various push-up plus exercises with and without sling in subjects with scapular dyskinesis. Methods: Total 18 male subjects with scapular dyskinesis were recruited. The UT, LT, and LSA electromyographic activities and the UT/LSA and UT/LT EMG activity ratios were measured during three push-up plus exercises with and without sling. Two-way repeated of analysis of variance was used to determine the statistical significance. Results: The UT activity was significantly lower in all postures without sling than that with sling. In addition, the LSA activity was significantly greater without than with sling, and significantly large in SPP, Low back supported push-up plus (LSPP), and Quadruped push-up plus. Additionally, the UT/LSA and UT/LT activity ratios were lower in SPP and LSPP without sling than with the other four push-up plus exercises. Conclusion: The push-up plus without sling were considered to decrease UT and increase LSA activity compared with exercises with sling. Furthermore, SPP without sling seems to be a more effective exercise for increasing LSA activity and lowering the UT/LSA and UT/LT activity ratios in scapular dyskinesis subjects.

Abstract
 Introduction
 Methods
  Subjects
  Scapular dyskinesis assessment
  Surface electromyography (EMG)
  Experimental procedure
  Statistical analysis
 Results
 Discussion
 Conclusion
 References

• Dong-hun Lee(Dept. of Physical Therapy, The Graduate School, Yonsei University)
• Heon-seock Cynn(Dept. of Physical Therapy, College of Health Science, Yonsei University, Dept. of Ergonomic Therapy, The Graduate School of Health and Environment, Yonsei University)
• Tae-lim Yoon(Department of Physical Therapy, College of Health Science, Cheongju University)
• Ji-hyun Lee(Dept. of Physical Therapy, The Graduate School, Yonsei University) Corresponding author