We studied the coordinated action of fingers during static tasks involving exertion of force and torque on a handheld object. Subjects were asked to keep a handle with an attachment that allowed for independent change of the suspended load (0.5–2.0 kg) and external torque (0.375–1.5 N m) in a vertical position while applying minimal effort. Normal and shear forces were measured from the thumb; normal forces only were measured from the four fingers.Experimental results(1) the thumb shear force increased during supination efforts and decreased during pronation efforts; (2) the total moment of the normal finger forces only counterbalanced approximately 50% of the external torque, hence shear forces accounted for approximately one-half of the total torque exerted on the object; (3) the total normal force increased with external torque, and the total force magnitude did not depend on the torque direction; (4) the forces of the ‘peripheral’ (index and little) fingers depended mainly on the torque while the forces exerted by the ‘central’ (middle and ring) fingers depended both on the load and torque; (5) there was a monotonic relationship between the mechanical advantage of a finger (i.e., its moment arm during torque production) and the force produced by that finger; and (6) antagonist finger moments acting opposite to the intended direction of the total moment were always observed –at low torques the antagonist moments were as high as 40–60% of the agonist moments.
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机译：我们研究了静态任务中手指的协调动作，这些静态任务涉及在手持对象上施加力和扭矩。要求受试者在垂直方向上保持附有手柄的附件，该附件可以独立改变悬吊负载（0.5–2.0 kg）和外部扭矩（0.375–1.5 N m），同时力求最小。从拇指测量法向力和剪切力；实验结果：（1）旋后动作时拇指剪切力增大，旋前动作时拇指剪切力减小。 （2）正常手指力的总力矩仅抵消了外部扭矩的大约50％，因此剪切力约占施加在物体上的总扭矩的一半； （3）总法向力随外力转矩的增加而增大，而总力大小与转矩方向无关。 （4）“周边”（食指和小指）的力主要取决于扭矩，而“中央”（中指和无名指）的手指所施加的力则既取决于载荷又取决于扭矩； （5）手指的机械优势（即在产生扭矩时的力矩臂）与该手指产生的力之间存在单调关系； （6）始终观察到与总力矩的预期方向相反的拮抗手指力矩–在低扭矩下，拮抗力矩高达激动剂力矩的40–60％。
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