Martin Joel R, Latash Mark L, Zatsiorsky Vladimir M
Department of Kinesiology, Pennsylvania State University, University Park, PA, USA.
J Appl Biomech. 2011 May;27(2):87-98. doi: 10.1123/jab.27.2.87.
This study investigated the effects of modifying contact finger forces in one direction-normal or tangential-on the entire set of the contact forces, while statically holding an object. Subjects grasped a handle instrumented with finger force-moment sensors, maintained it at rest in the air, and then slowly: (1) increased the grasping force, (2) tried to spread fingers apart, and (3) tried to squeeze fingers together. Analysis was mostly performed at the virtual finger (VF) level (the VF is an imaginable finger that generates the same force and moment as the four fingers combined). For all three tasks there were statistically significant changes in the VF normal and tangential forces. For finger spreading/squeezing the tangential force neutral point was located between the index and middle fingers. We conclude that the internal forces are regulated as a whole, including adjustments in both normal and tangential force, instead of only a subset of forces (normal or tangential). The effects of such factors as EFFORT and TORQUE were additive; their interaction was not statistically significant, thus supporting the principle of superposition in human prehension.
本研究调查了在静态握持物体时,沿一个方向(法线方向或切线方向)改变接触手指力对整个接触力集合的影响。受试者握住一个装有手指力 - 力矩传感器的手柄,将其在空中保持静止,然后缓慢地:(1) 增加握力,(2) 尝试分开手指,以及 (3) 尝试挤压手指。分析主要在虚拟手指(VF)水平进行(虚拟手指是一个可想象的手指,其产生的力和力矩与四根手指组合产生的相同)。对于所有三项任务,虚拟手指的法线和切线力都有统计学上的显著变化。对于手指分开/挤压,切线力中性点位于食指和中指之间。我们得出结论,内力作为一个整体进行调节,包括法线力和切线力的调整,而不是仅调整一部分力(法线力或切线力)。诸如力和扭矩等因素的影响是相加的;它们的相互作用在统计学上不显著,从而支持了人类抓握中的叠加原理。