Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen, Antonius Deusinglaan 1, 9713, AV, Groningen, The Netherlands.
Sci Rep. 2019 Nov 22;9(1):17378. doi: 10.1038/s41598-019-53913-9.
During rhythmic pointing movements, degrees of freedom (DOF) in the human action system-such as joint-angles in the arm-are assumed to covary to stabilise end-effector movement, e.g. index finger. In this paper, it is suggested that the end-effector movement and the coordination of DOF are reciprocally related in synergies that link DOF so as to produce the end-effector movement. The coordination of DOF in synergies and the relation between end-effector movement and DOF coordination received little attention, though essential to understand the principles of synergy formation. Therefore, the current study assessed how the end-effector movement related to the coordination of joint-angles during rhythmic pointing across target widths and distances. Results demonstrated that joint-angles were linked in different synergies when end-effector movements differed across conditions. Furthermore, in every condition, three joint-angles (shoulder plane of elevation, shoulder inward-outward rotation, elbow flexion-extension) largely drove the end-effector, and all joint-angles contributed to covariation that stabilised the end-effector. Together, results demonstrated synergies that produced the end-effector movement, constrained joint-angles so that they covaried to stabilise the end-effector, and differed when end-effector movement differed. Hence, end-effector and joint-angles were reciprocally related in synergies-indicating that the action system was organised as a complex dynamical system.
在有节奏的指向运动中，人类动作系统的自由度（DOF）——例如手臂中的关节角度——被认为是相互关联的，以稳定末端效应器的运动，例如食指。本文提出，末端效应器的运动和 DOF 的协调在协同作用中是相互关联的，这些协同作用将 DOF 联系起来，以产生末端效应器的运动。协同作用中 DOF 的协调以及末端效应器运动和 DOF 协调之间的关系受到的关注较少，但对于理解协同作用形成的原则至关重要。因此，本研究评估了在不同目标宽度和距离的有节奏的指向运动中，末端效应器的运动与关节角度的协调之间的关系。结果表明，当末端效应器在不同条件下运动时，关节角度在不同的协同作用中相互关联。此外，在每种条件下，三个关节角度（肩的矢状面抬高、肩的内收-外展旋转、肘的屈伸）主要驱动末端效应器，所有关节角度都有助于稳定末端效应器的协变。总之，结果表明协同作用产生了末端效应器的运动，约束了关节角度，使它们协变以稳定末端效应器，并且当末端效应器的运动不同时，协同作用也会有所不同。因此，末端效应器和关节角度在协同作用中是相互关联的，这表明动作系统是作为一个复杂的动力系统组织的。
