Limb Stiffness Is Modulated With Spatial Accuracy Requirements During Movement in the Absence of Destabilizing Forces

• Published in: Journal of neurophysiology 2009-03, Vol.101 (3), p.1542-1549
• Main Authors: Wong, Jeremy, Wilson, Elizabeth T, Malfait, Nicole, Gribble, Paul L
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Adolescent; Adult; Biomechanical Phenomena; Coriolis Force; Electromyography - methods; Extremities - physiology; Female; Humans; Male; Movement - physiology; Proprioception; Psychomotor Performance - physiology; Young Adult
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.91188.2008

1 Department of Psychology, 2 Graduate Program in Neuroscience, and 3 Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada Submitted 5 November 2008; accepted in final form 8 January 2009 Abstract The motor system can use a number of mechanisms to increase movement accuracy and compensate for perturbing external forces, interaction torques, and neuromuscular noise. Empirical studies have shown that stiffness modulation is one adaptive mechanism used to control arm movements in the presence of destabilizing external force loads. Other work has shown that arm muscle activity is increased at movement end for reaching movements to small visual targets and that changes in stiffness at movement end are oriented to match changes in visual accuracy requirements such as target shape. In this study, we assess whether limb stiffness is modulated to match spatial accuracy requirements during movement, conveyed using visual stimuli, in the absence of external force loads. Limb stiffness was estimated in the middle of reaching movements to visual targets located at the end of a narrow (8 mm) or wide (8 cm) visual track. When greater movement accuracy was required, we observed modest but reliable increases in limb stiffness in a direction perpendicular to the track. These findings support the notion that the motor system uses stiffness control to augment movement accuracy during movement and does so in the absence of external unstable force loads, in response to changing accuracy requirements conveyed using visual cues. Address for reprint requests and other correspondence: P. L. Gribble, Department of Psychology, The University of Western Ontario, 1151 Richmond St., London, ON, Canada N6A 5C2 (E-mail: pgribble{at}uwo.ca )