Effects of core stability on shoulder and spine kinematics during upper limb elevation: A sex-specific analysis

Background: Upper limb elevation begins with core stabilization, but the effects of core stability on shoulder and spine kinematics are unknown. Sex differences also exist in shoulder kinematics and core stability. Objective: To clarify the effects of core stability on shoulder and spine kinematics during upper limb elevation by taking sex into account. Design: Cross-sectional. Methods: The Sahrmann Core Stability Test, lumbar spine motor control test battery, and Y Balance Test (lower and upper quarters) were performed in 50 healthy young adults. For each test, a principal component (PC) analysis was conducted according to sex; the overall core stability score was calculated. The top and bottom third of the PC scores were defined as high and low score groups, respectively (each group: nine males and eight females). Shoulder and spine kinematics during upper limb elevation were compared separately for males and females. Results: Spinal extension was greater in the low score group by a maximum of 1.9? in males (P < .001; eta(2) = 0.068) and 1.6? in females (P < .001; eta(2 )= 0.141). In the low score group of females, the scapular posterior tilt was a maximum of 5.6? smaller (P < .001; eta(2) = 0.221) and glenohumeral elevation was a maximum of 4.5? larger (P < .001; eta(2) = 0.113) than the high score group of females. Conclusion: Core stability affected spine and female scapular and glenohumeral kinematics during upper limb elevation. Core stability may be one of the potential contributors to shoulder kinematics, particularly in females.