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In this paper we describe how a theory of posture-based motion planning recently applied to human grasping may contribute to the understanding of grasping pathology. The theory is implemented as a computer model rendered as a stick-figure animation capable of generating realistic multi-joint grasping movements. As shown here, the model can also be used to simulate grasping movements whose kinematics resemble those of grasps performed by people with spastic hemiparesis. The simulations demonstrate effects of: (a) reduced ranges of motion of arm joints on the size of the reachable workspace, (b) awkward starting postures on me time course of the hand closing around an object, (c) increased costs of joint rotations on movement time, and (d) addition of noise to biphasic joint rotations on the low-velocity phase of wrist transport.
R.G.J. Meulenbroek is with the Nijmegen Institute for Cognition and Information, P.O. Box 9104,6500 HE Nijmegen, The Netherlands. D.A. Rosenbaum is with the Department of Psychology at Pennsylvania State University, University Park, PA 16802-3408. J. Vaughan is with the Department of Psychology at Hamilton College, Clinton, NY 13323. The article is based on a talk presented at the International Workshop on Studies and Models of Human Prehension; Contributions to Understanding Grasping Pathology, Werkenrode, Groesbeek, The Netherlands, January 13, 2000.