Abstract
The purpose of this study was to describe three-dimensional scapular translation and rotation during arm elevation. Thirteen male subjects performed humeral elevation in the scapular plane. The location of the center of mass (CoM) of the scapula was determined using the existing skeletal model of the scapula. Based on the helical axis, the scapular rotation axis were computed. During humeral elevation, a) the position of the CoM of the scapula relative to the thorax moved superiorly and medially, b) the lateral (upward) rotation and posterior tilt angles of the scapular attitude were changed at a constant rate, c) the orientation of the scapular rotation axis was nearly constant, d) the location of the scapular rotation center on the scapula moved medially from the acromion. These results indicate the mechanical relationship in which the time-history of the rotation axis orientation and position determine the attitude and position of the CoM at any given instant during the scapular motion of interest.
