Influence of object weight and terminal orientation on upper limb postures during grasping, holding, and placing cylindrical object
Authors: Wei Zhou, Thomas J. Armstrong, Diana M. Wegner, Matthew P. Reed.
This study examines the effect of object weight and terminal orientation on upper limb postures during grasping, holding, and placing cylindrical objects. An experiment including two sessions was conducted. In the first session, eight subjects grasped and held a horizontally located cylindrical object with varying weights (0.34, 2.04, 3.74, and 5.44 kg) using self-selected postures, then placed the object with selfselected target location and orientation. In the second session, five subjects grasped and held cylindrical object with varying weights, then positioned the object at a target location with specified orientation, i.e., either left or right end down. Eight posture categories for grasping the cylindrical object were identified based on upper limb posture. Multiple postural strategies for grasping, holding, and placing the objects were observed, influenced by an interaction between object weight and terminal orientation. These results show that posture selection in these tasks is influenced by force exertion and how the object is to be positioned.