Department of Kinesiology, University of Maryland, College Park, MD 20742, USA.
Hum Mov Sci. 2010 Feb;29(1):19-34. doi: 10.1016/j.humov.2009.11.001. Epub 2010 Jan 8.
Previous studies have shown that the interactions of human hand digits are influenced by internal constraints, i.e., biomechanical and central constraints. However, little is currently known about the influence of externally imposed mechanical constraints on multi-finger behavior. This study investigates maximal digit force production during fixed object and free object prehension in statics. The results from the fixed object prehension indicated that the closer the non-task finger was positioned to the task finger, the greater the force produced by the non-task finger, which supports the proximity hypothesis. Conversely, the non-task fingers with longer moment arms showed greater force production during free object prehension, which supports the mechanical advantage hypothesis. During the free object prehension, equal and opposite torques were produced by the digit normal forces and tangential forces, while this phenomenon was not observed in the fixed object prehension. The results also showed that the thumb normal force had a positive linear relationship with task-finger normal forces during fixed object prehension while the thumb normal force remained constant during free object prehension tasks. We concluded that the CNS employed different strategies when different sets of internal and external constraints are provided during multi-digit prehension tasks.
先前的研究表明，人手各指之间的相互作用受到内部约束的影响，即生物力学和中枢约束的影响。然而，目前对于外部施加的机械约束对多指行为的影响知之甚少。本研究在静态中调查了固定物体和自由物体抓取过程中最大手指力的产生。固定物体抓取的结果表明，非任务手指越靠近任务手指，非任务手指产生的力就越大，这支持了接近假说。相反，在自由物体抓取过程中，具有较长力臂的非任务手指产生更大的力，这支持了机械优势假说。在自由物体抓取过程中，手指的法向力和切向力产生相等且相反的扭矩，而在固定物体抓取中则没有观察到这种现象。结果还表明，在固定物体抓取过程中，拇指的法向力与任务手指的法向力呈正线性关系，而在自由物体抓取任务中，拇指的法向力保持不变。我们得出结论，中枢神经系统在多指抓取任务中提供不同的内部和外部约束时，采用了不同的策略。
