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 trapeziusand the serratus anterior muscles during diverse shoulder abduction exercises applied withvibrations in order to determine the appropriate exercise methods for recovery of scapularmuscle balance. [Subjects and Methods] Twenty-four subjects voluntarilyparticipated in this study. The subjects performed shoulder abduction at various shoulderjoint abduction angles (90°, 120°, 150°, 180°) with oscillation movements. [Results] At120°, all the subjects showed significant increases in the muscle activity of the serratusanterior muscle in comparison with the upper trapezius muscle. However, no significantdifference was found at angles other than 120°. [Conclusion] To selectively strengthen theserratus anterior, applying vibration stimuli at the 120° shoulder abduction position isconsidered to be appropriate.Key words: Serratus anterior, Upper trapezius, Vibration