The Effects of Lower Limb Extension in the Prone Position on the Activity of the Contralateral Fibers of the Lower Trapezius Muscle with Respect to Changes in the Abduction Angle of the Shoulder Joint

: [Purpose] The purpose of this study was to investigate how alteration of the shoulder abduction angle affects the muscle activity of the lower trapezius muscle fibers while the hip joint is extended in the prone position. [Subjects] Sixteen healthy males participated in this study. [Methods] With the hip joint extended in the prone position, we measured the muscle activity of the lower trapezius muscle fibers at different abduction angles of the shoulder joint. [Results] The muscle activity of the lower trapezius muscle fibers was significantly increased at shoulder joint abduction of 90 and 120°compared with shoulder joint abduction of 0, 30 and 60°. [Conclusions] The results suggest that the lower trapezius muscle fibers contribute to upward rotation of the scapula in order to utilize the upper limb’s weight.