The effects of shoulder joint abduction angles on the muscle activity of the serratus anterior muscle and the upper trapezius muscle while vibrations are applied

[Purpose] The purpose of this study was to examine the ratio between the upper trapezius and the serratus anterior muscles during diverse shoulder abduction exercises applied with vibrations in order to determine the appropriate exercise methods for recovery of scapular muscle balance. [Subjects and Methods] Twenty-four subjects voluntarily participated in this study. The subjects performed shoulder abduction at various shoulder joint abduction angles (90°, 120°, 150°, 180°) with oscillation movements. [Results] At 120°, all the subjects showed significant increases in the muscle activity of the serratus anterior muscle in comparison with the upper trapezius muscle. However, no significant difference was found at angles other than 120°. [Conclusion] To selectively strengthen the serratus anterior, applying vibration stimuli at the 120° shoulder abduction position is considered to be appropriate.