Do Arm Postures Vary With the Speed of Reaching?

  1 Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011; and   2 Department of Neuroscience, University of Minnesota Medical School, Minneapolis, Minnesota 55455 Nishikawa, Kiisa C., Sara T. Murray, and Martha Flanders. Do Arm Postures Vary With the Speed of Reac...

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Bibliographic Details
Published in:Journal of neurophysiology 1999-05, Vol.81 (5), p.2582-2586
Main Authors: Nishikawa, Kiisa C, Murray, Sara T, Flanders, Martha
Format: Article
Language:English
Subjects:
Arm - physiology
Female
Humans
Male
Memory - physiology
Movement - physiology
Photic Stimulation
Posture - physiology
Psychomotor Performance - physiology
Space life sciences
Time Factors
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Summary:  1 Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011; and   2 Department of Neuroscience, University of Minnesota Medical School, Minneapolis, Minnesota 55455 Nishikawa, Kiisa C., Sara T. Murray, and Martha Flanders. Do Arm Postures Vary With the Speed of Reaching?. J. Neurophysiol. 81: 2582-2586, 1999. Do arm postures vary with the speed of reaching? For reaching movements in one plane, the hand has been observed to follow a similar path regardless of speed. Recent work on the control of more complex reaching movements raises the question of whether a similar "speed invariance" also holds for the additional degrees of freedom. Therefore we examined human arm movements involving initial and final hand locations distributed throughout the three-dimensional (3D) workspace of the arm. Despite this added complexity, arm kinematics (summarized by the spatial orientation of the "plane of the arm" and the 3D curvature of the hand path) changed very little for movements performed over a wide range of speeds. If the total force (dynamic + quasistatic) had been optimized by the control system (e.g., as in a minimization of the change in joint torques or the change in muscular forces), the optimal solution would change with speed; slow movements would reflect the minimal antigravity torques, whereas fast movements would be more strongly influenced by dynamic factors. The speed-invariant postures observed in this study are instead consistent with a hypothesized optimization of only the dynamic forces.
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.1999.81.5.2582