Characterizing human hand prehensile strength by force and moment wrench.

Characterizing human hand capabilities or demand created by various occupational tasks or activities of daily living has been mainly accomplished by measuring the maximum force exerted on a force dynamometer in a number of standard grips, for example power, key pinch and tip pinch grips. A framework is proposed instead to characterize human hand prehensile strength in generic form by describing external force and moment wrench capability, where a wrench is a vector describing the forces and moments applied at a point. It is further suggested that if tools and activities are characterized by the internal forces and external forces and moments required, a better understanding of the human prehension in occupational settings and during activities of daily living can be obtained. An example of using a pistol grip drill is used to show the utility of the approach.