The effect of instruction and hand dominance on grip force coordination in manipulation tasks

Date
2011
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University of Delaware
Abstract
The ability to grasp and hold an object is not only one of the most common daily activities but also essential for living an independent life. According to a simple prehension model, the force applied upon a vertically oriented hand-held object could be decomposed into two distinctive but highly coordinated components: the grip force (GF; the component perpendicular to the hand-object contact area that provides friction) and the load force (LF; the component parallel to the hand-object contact area that can either move the object or support of the body). The GF-LF coordination could be affected by a number of factors that still remain underexplored. The aim of this study is to investigate the effect of instructions and hand dominance on the relationship of GF and LF. Sixteen right-handed participants were tested on a custom designed instrumented device. They performed bimanual manipulation tasks under different instructions and mechanical conditions. The exerted GF and LF were recorded and analyzed. Indices of GF scaling, GF-LG coupling and GF modulation were calculated separately for the dominant and non-dominant hand. The result showed that the instruction of "pull" leads to higher GF-LF coordination than the instruction of "hold", as seen by a lower GF/LF ratio, higher GF-LF coupling, and higher GF modulation. The only effect of hand dominance was a more prominent time-lag of GF of the non-dominant hand. Overall, the observed findings suggest that the instructions could play an important role in GF-LF coordination, and, therefore, they should be taken into account when either studying hand manipulation activities in healthy individuals or testing hand function in various patient populations.
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