The Effects of Hip Position on Scapular Kinematics and Muscle Activation in the Oblique Sling: A Simulated Study

The purpose of this study was to measure differences in scapular kinematics and muscular activation, associated with shoulder stabilization and the oblique sling, as a result of changes in hip position. Scapular kinematics and muscular activation of the latissimus dorsi, infraspinatus, upper trapezius, lower trapezius, serratus anterior, and the contralateral gluteus maximus were measured during scapular plane humeral elevation. Subjects (n=25 male and female) were required to elevate the dominant arm up to 120º while remaining in the scapular plane and performed the following conditions in randomized order: standing bilateral hip extension, seated bilateral hip flexion, and seated unilateral hip flexion of the contralateral leg. A 3-way ANOVA was conducted to assess the interaction between degree of humeral elevation, condition, and muscle. Results I: Acute enhancement of scapular kinematics and muscle activation was not of statistical significance. The findings of this study do not support the involvement of the thoracolumbar fascia in force transmission between the gluteus maximus and the contralateral shoulder. Results II: Enhancement of scapular kinematics and muscle activation was of statistical significance. Since hip position affects shoulder motion practitioners might consider this in the rehabilitation of generalized shoulder injuries.