Vigouroux Laurent, Domalain Mathieu, Berton Eric
Movement Sciences Institute, Etienne Jules Marey, UMR 6233, Mediterranean University, Marseille, France.
J Appl Biomech. 2011 Aug;27(3):173-80. doi: 10.1123/jab.27.3.173.
The objective of this study was to identify the impact of modifying the object width on muscle and joint forces while gripping objects. The experimental protocol consisted to maintain horizontally five objects of different widths (3.5, 4.5, 5.5, 6.5, and 7.5 cm) with a thumb-index finger grip. Subjects were required to grasp spontaneously the object without any instruction regarding the grip force (GF) to apply. A biomechanical model of thumb-index finger pinch was developed to estimate muscle and joint forces. This model included electromyography, fingertip force, and kinematics data as inputs. The finger joint postures and the GF varied across the object widths. The estimated muscle forces also varied significantly according to the object width. Interestingly, we observed that the muscle force/GF ratios of major flexor muscles remain particularly stable with respect to the width whereas other muscle ratios differed largely. This may argue for a control strategy in which the actions of flexors were preserved in spite of change in joint postures. The estimated joint forces tended to increase with object width and increased in the distal-proximal sense. Overall, these results are of importance for the ergonomic design of handheld objects and for clinical applications.
本研究的目的是确定在抓握物体时改变物体宽度对肌肉和关节力的影响。实验方案包括用拇指-食指抓握水平放置的五个不同宽度（3.5、4.5、5.5、6.5和7.5厘米）的物体。受试者被要求自发抓握物体，且未给出关于施加握力（GF）的任何指示。开发了一个拇指-食指捏合的生物力学模型来估计肌肉和关节力。该模型将肌电图、指尖力和运动学数据作为输入。手指关节姿势和握力随物体宽度而变化。估计的肌肉力也根据物体宽度而有显著变化。有趣的是，我们观察到主要屈肌的肌肉力/握力比值相对于宽度保持特别稳定，而其他肌肉比值差异很大。这可能支持一种控制策略，即尽管关节姿势发生变化，屈肌的动作仍得以保留。估计的关节力倾向于随着物体宽度增加，并且从远端到近端方向增加。总体而言，这些结果对于手持物体的人体工程学设计和临床应用具有重要意义。
