Influence of reducing anterior pelvic tilt on shoulder posture and the electromyographic activity of scapular upward rotators.

BACKGROUND: Modifications of posture in a segment may influence the posture of adjacent and nonadjacent segments and muscular activity. The spine-shoulder and spine-pelvis relationships suggest that the pelvis may influence shoulder posture.

OBJECTIVE: To investigate the effect of the active reduction of the anterior pelvic tilt on shoulder and trunk posture during static standing posture and on the electromyographic activity of the scapular upward rotators during elevation and lowering of the arm.

METHODS: Thirty-one young adults were assessed in a relaxed standing position and a standing position with 30% active reduction of the anterior pelvic tilt. The pelvic tilt, trunk posture, and forward shoulder posture during the static standing posture and the electromyographic activity during elevation and lowering of the arm were assessed.

RESULTS: Paired t-tests indicated that the active reduction of the anterior pelvic tilt reduced the trunk extension (MD=1.09; 95%CI=-2.79 to -1.03). There were no effects on the forward shoulder posture (MD=0.09; 95%CI=-0.92 to 1.09). Repeated measures of analyses of variance indicated an increase in lower trapezius electromyographic activity (MD=3.6; 95%CI=1.28 to 5.92). There was a greater reduction in upper trapezius activity after pelvic tilt reduction during arm elevation (MD=1.52%; 95%CI=-2.79 to -0.25) compared to that during the lowering phase. There were no effects of pelvic tilt reduction on the electromyographic activity of the serratus anterior (MD=3.26; 95%CI=-3.36 to 9.87).

CONCLUSION: The influence of pelvic posture on the trunk posture and lower trapezius activation should be considered when assessing or planning exercise for individuals with shoulder or trunk conditions.