EFFECTS OF CORE STABILITY ON SHOULDER AND SPINE KINEMATICS DURING UPPER LIMB ELEVATION: ASEX-SPECIFIC ANALYSIS

M. Kuniki¹, Y. Iwamoto², N. Kito³

¹Graduate School of Medical Welfare Sciences, Medical Engineering, Hiroshima International University, Higashi-Hiroshima, Japan, ²Graduate School of Biomedical and Health Sciences, Hiroshima University, Department of Neuromechanics, Hiroshima, Japan, ³Faculty of Rehabilitation, Hiroshima International University, Department of Rehabilitation, Hiroshima, Japan

Background: Upper limb elevation begins with core stabilization, but the effects of core stability on shoulder and spine kinematics are unknown. Although several studies have shown a relationship between poor core stability and shoulder injuries, there is much that is unknown about the biomechanical mechanism, which may influence clinical decision-making. Sex differences also exist in shoulder kinematics and core stability. We believed that it was necessary to include sex in our analysis of the effects of core stability on shoulder and spine kinematics.

Purpose: To clarify the effects of core stability on shoulder and spine kinematics during upper limb elevation by taking sex into account.

Methods: TheSahrmann Core Stability Test, lumbar spine motor control test battery, Lower Quarter Y Balance Test and Upper Quarter Y Balance Test 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). The participantsthen performedupper limbelevationinthescapular planeduring which the kinematics of the humerus, scapula, and spine were calculated usingan electromagnetic tracking device and a three-dimensional motion capture system. A two-way analysis of variancewas used to examine the main effect of group and the interaction between group and elevation time. The effect size (partial η²) was calculated using three suggested cutoff points: small, <0.06; medium, 0.06–0.14; and large, >0.14). An alpha level of <0.05 was considered in all statistical tests.

Results: Spinal extension was greater in the low score group by a maximum of 1.9° in males (P < .001; η²= .068) and 1.6° in females (P < .001; η²= .141). In the low score group of females, the scapular posterior tilt was a maximum of 5.6° smaller (P < .001; η²= .221) and glenohumeral elevation was a maximum of 4.5° larger (P < .001; η²= .113) than the high score group of females. In shoulder kinematics, no main effect or interaction for any of the parameters was observed in males.

Conclusions: Core stability affected spine and female scapular andglenohumeral kinematicsduring upper limb elevation. Core stability may be one of the potential contributorsto shoulderkinematics, particularly in females. This partially supports the theory that poor core stability contributes to shoulder injury.

Implications: The need to consider core stability when assessing and treating scapular motion in clinical practice, especially in females, is suggested by this study.

Funding acknowledgements: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Keywords:
Shoulder
Spine
Core stability

Topics:
Musculoskeletal: upper limb
Musculoskeletal: spine
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: Hiroshima International University

Committee: Medical Research Ethics Committee

Ethics number: 20-021