Stiffness, not inertial coupling, determines path curvature of wrist motions

• DOI: 10.1152/jn.00428.2011
• Publication Date: 2011-12-02T05:54:31Z
• Authors: Steven K. Charles; Neville Hogan
• Keywords: Movement; 0206 medical engineering; 02 engineering and technology; Wrist; Models, Biological; Biomechanical Phenomena; Motion; Nonlinear Dynamics; Torque; Humans; Range of Motion, Articular; Gravitation

When humans rotate their wrist in flexion-extension, radial-ulnar deviation, and combinations, the resulting paths (like path of a laser pointer on screen) exhibit distinctive pattern curvature. In this report we show that passive stiffness is sufficient to account for pattern. Simulating dynamics rotations using demonstrably realistic model under variety conditions, can explain all characteristics observed We also provide evidence against other possible causes. further demonstrate phenomenon robust variations human parameters (inertia, damping, stiffness) choice inputs. Our findings two previously phenomena: why faster more curvature rotates with pronation-supination forearm. results imply that, as reaching, straightness goal planning control rotations. This requires predict compensate dynamics, but, unlike nonlinear inertial coupling (e.g., Coriolis acceleration) insignificant. The dominant term be compensated stiffness.