CUED Publications database

Impedance control balances stability with metabolically costly muscle activation.

Franklin, DW and So, U and Kawato, M and Milner, TE (2004) Impedance control balances stability with metabolically costly muscle activation. J Neurophysiol, 92. pp. 3097-3105. ISSN 0022-3077

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Abstract

Humans are able to stabilize their movements in environments with unstable dynamics by selectively modifying arm impedance independently of force and torque. We further investigated adaptation to unstable dynamics to determine whether the CNS maintains a constant overall level of stability as the instability of the environmental dynamics is varied. Subjects performed reaching movements in unstable force fields of varying strength, generated by a robotic manipulator. Although the force fields disrupted the initial movements, subjects were able to adapt to the novel dynamics and learned to produce straight trajectories. After adaptation, the endpoint stiffness of the arm was measured at the midpoint of the movement. The stiffness had been selectively modified in the direction of the instability. The stiffness in the stable direction was relatively unchanged from that measured during movements in a null force field prior to exposure to the unstable force field. This impedance modification was achieved without changes in force and torque. The overall stiffness of the arm and environment in the direction of instability was adapted to the force field strength such that it remained equivalent to that of the null force field. This suggests that the CNS attempts both to maintain a minimum level of stability and minimize energy expenditure.

Item Type: Article
Uncontrolled Keywords: Arm Female Humans Joints Learning Male Motor Activity Muscle, Skeletal Posture Restraint, Physical Torque
Subjects: UNSPECIFIED
Divisions: Div F > Computational and Biological Learning
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:24
Last Modified: 08 Dec 2014 02:13
DOI: 10.1152/jn.00364.2004