Weir P L, MacKenzie C L, Marteniuk R G, Cargoe S L, Frazer M B
Department of Kinesiology, University of Waterloo.
J Mot Behav. 1991 Sep;23(3):192-204. doi: 10.1080/00222895.1991.10118362.
The purpose of these experiments was to determine the effects of object weight and condition of weight presentation on the kinematics of human prehension. Subjects performed reaching and grasping movements to metal dowels whose visible characteristics were similar but whose weight varied (20, 55, 150, 410 g). Movements were performed under two conditions of weight presentation, random (weight unknown) and blocked (weight known). Three-dimensional movements of the thumb, index finger, and wrist were recorded, using a WATSMART system to obtain information regarding the grasp and transport components. The results of the first experiment indicated that object weight and condition of presentation affected the temporal and kinematic measures for both the grasp and transport components. In conjunction with the results of a second experiment, in which time in contact with the dowel was measured, it was shown that the free-motion phase of prehension (i.e., up to object contact) was invariant over the different conditions, however. The changes were observed in the finger-object interaction phase (when subjects applied forces after contact with the dowel), prior to lift-off. These results were interpreted as indicating (a) object weight does not influence the planning and execution of the free-motion phase of prehension and (b) there are at least two motor control phases involved in prehension, one for making contact with the object and the other for finger-object interaction. The changing contributions of visual, kinesthetic, and haptic information during these two phases is discussed.
这些实验的目的是确定物体重量及重量呈现条件对人类抓握运动学的影响。受试者对金属棒进行伸手抓握动作，这些金属棒的外观特征相似，但重量不同（20、55、150、410克）。动作在两种重量呈现条件下进行，即随机呈现（重量未知）和分组呈现（重量已知）。使用WATSMART系统记录拇指、食指和手腕的三维运动，以获取有关抓握和运输部分的信息。第一个实验的结果表明，物体重量和呈现条件会影响抓握和运输部分的时间及运动学指标。结合第二个实验的结果（该实验测量了与金属棒接触的时间），结果表明，抓握的自由运动阶段（即直到与物体接触）在不同条件下是不变的。然而，在手指与物体相互作用阶段（即受试者在与金属棒接触后施加力时），在提起物体之前观察到了变化。这些结果被解释为表明：（a）物体重量不影响抓握自由运动阶段的计划和执行；（b）抓握至少涉及两个运动控制阶段，一个用于与物体接触，另一个用于手指与物体的相互作用。本文还讨论了在这两个阶段视觉、动觉和触觉信息的变化作用。
