The Effect of Hand Position Changes on Electromyographic Activity of Shoulder Stabilizers during Push-up Plus Exercise on Stable and Unstable Surfaces.

[Purpose] The purpose of this study was to determine the effect of hand position changes on electromyographic activity of shoulder stabilizers during push-up plus exercise (PUPE) performed on both stable and unstable surfaces. [Subjects] This study was performed on a cohort of 20 normal adults divided into an unstable surface group (USG) (n=10) and a stable surface group (SSG) (n=10). [Methods] A sling device was used to provide an unstable surface, and a push-up bar was used to provide a stable surface. PUPEs were performed with hands in various positions: the neutral position (NP), the internal rotation position (IRP), or the external rotation position (ERP). Electromyography was used to determine and analyze the electromyographic activity of the upper trapezius muscle (UT), the lower trapezius muscle (LT), the serratus anterior muscle (SA), and the pectoralis major muscle (PM). [Results] Comparison of the results within the USG and SSG showed significant differences depending on the hand position used during the exercise. Comparison between the USG and SSG showed that the ERP hand posture resulted in significant differences in electromyographic activity of the SA in the USG. [Conclusion] The electromyographic activity of the SA indicated that performing PUPEs using the ERP on an unstable surface provided more effective intervention for shoulder stabilization than ERP on a stable surface.