Grinyagin I V, Biryukova E V, Maier M A
Russian State Medicine University, Moscow.
J Neurophysiol. 2005 Oct;94(4):2284-94. doi: 10.1152/jn.01310.2004. Epub 2005 May 25.
We analyzed the adaptability of human thumb and index finger movement kinematics and dynamics to variations of precision grip aperture and movement velocity. Six subjects performed precision grip opening and closing movements under different conditions of movement velocity and movement aperture (thumb and index finger tip-to-tip distance). Angular motion of the thumb and index finger joints was recorded with a CyberGlove and a three-dimensional biomechanical model was used for solving the inverse dynamics problem during precision grip movements, i.e., for calculating joint torques from experimentally obtained angular variations. The time-varying joint angles and joint torques were analyzed by principal-component analysis to quantify the contributions of individual joints in kinematic and dynamic synergies. At the level of movement kinematics, we found subject-specific angular contributions. However, the adaptation to large aperture, achieved by an increase of the relative contribution of the proximal joints, was subject-invariant. At the level of movement dynamics, the adaptation of thumb-index finger movements to task constraints was similar among all subjects and required the linear scaling of joint torques, the synchronization of joint torques under high velocity conditions, and a flexible redistribution of joint torques between the proximal joint of the thumb and that of the index finger. This work represents one of the first attempts at calculating the joint torques during human precision-grip movements and indicates that the dynamic synergies seem to be remarkably simple compared with the synergies found for movement kinematics.
我们分析了人类拇指和食指运动的运动学和动力学对精确抓握孔径和运动速度变化的适应性。六名受试者在不同运动速度和运动孔径（拇指和食指指尖间距离）条件下进行精确抓握的开合运动。使用CyberGlove记录拇指和食指关节的角运动，并使用三维生物力学模型来解决精确抓握运动期间的逆动力学问题，即根据实验获得的角度变化计算关节扭矩。通过主成分分析对随时间变化的关节角度和关节扭矩进行分析，以量化各个关节在运动学和动力学协同作用中的贡献。在运动运动学层面，我们发现了个体特异性的角度贡献。然而，通过增加近端关节的相对贡献来实现对大孔径的适应是个体不变的。在运动动力学层面，所有受试者中拇指 - 食指运动对任务约束的适应是相似的，并且需要关节扭矩的线性缩放、高速条件下关节扭矩的同步以及拇指近端关节和食指近端关节之间关节扭矩的灵活重新分配。这项工作是计算人类精确抓握运动期间关节扭矩的首批尝试之一，并且表明与运动运动学中发现的协同作用相比，动态协同作用似乎非常简单。
