2021 年 67 巻 3 号 p. 264-271
Objective To investigate the effects of head position on scapular orientation in a posture of simulated rugby tackling.
Design Laboratory experimental study.
Methods Twenty-nine healthy young men lay on the edge of a wooden rigid bed in the prone position with their dominant arm free. The experimental arm movement task was conducted in four head positions (2 neck bending x 2 neck rotation) with maximum ranges of direction: the dominant arm was rotated from an intermediate position to maximum external rotation at 90° shoulder abduction with 90° elbow flexion while maintaining each neck position. During the tasks, dynamic scapular orientations were measured with an electromagnetic sensor system.
Results In total, 348 experimental trials were included in the analyses. Two-way repeated-measures analysis of variance demonstrated that the direction of neck bending and the side of neck rotation relative to the arm movement significantly affected the scapular orientation. The scapular tilting angle was significant during neck rotation ipsilateral to the arm movement (mean difference, 11°). The scapular upward rotation angle was higher during neck rotation contralateral than ipsilateral rotation to the arm movement (mean difference, 2.5°) regardless of the neck bending position. The scapular external rotation angle was significant during neck rotation ipsilateral to the arm movement (mean difference, 5.5°).
Conclusions The neck position affects the scapular orientation in the prone position. Neck flexion with rotation contralateral to the arm movement represents an anteriorly tilted and internally rotated scapula orientation, which may increase the risk of shoulder injury such as dislocation.
