Computational and Mathematical Methods in Medicine
Volume 2012 (2012), Article ID 975735, 9 pages
Research Article

Dynamic Variability of Isometric Action Tremor in Precision Pinching

1Motor Behavior Laboratory, Department of Kinesiology and Health Education, The University of Texas at Austin, 1 University Station, Mail Stop D3700, Austin, TX 78712, USA
2Department of Kinesiology, University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117, USA

Received 25 June 2012; Accepted 28 August 2012

Academic Editor: Guang Wu

Copyright © 2012 Tim Eakin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Evolutionary development of isometric force impulse frequencies, power, and the directional concordance of changes in oscillatory tremor during performance of a two-digit force regulation task was examined. Analyses compared a patient group having tremor confounding volitional force regulation with a control group having no neuropathological diagnosis. Dependent variables for tremor varied temporally and spatially, both within individual trials and across trials, across individuals, across groups, and between digits. Particularly striking findings were magnitude increases during approaches to cue markers and shifts in the concordance phase from pinching toward rigid sway patterns as the magnitude increased. Magnitudes were significantly different among trace line segments of the task and were characterized by differences in relative force required and by the task progress with respect to cue markers for beginning, reversing force change direction, or task termination. The main systematic differences occurred during cue marker approach and were independent of trial sequence order.