van Mourik Anke M, Beek Peter J
Institute for Fundamental and Clinical Human Movement Sciences, Free University, Amsterdam, The Netherlands.
Acta Psychol (Amst). 2004 Oct;117(2):121-38. doi: 10.1016/j.actpsy.2004.06.001.
In the literature on motor control, three theoretical perspectives on the relation between discrete and cyclical movements may be discerned: (a) cyclical movements are concatenated discrete movements; (b) discrete movements are a limiting case of cyclical movements, and (c) discrete and cyclical movements are motor primitives that may be combined but are irreducible to each other. To examine the tenability of these perspectives, 16 participants performed cyclical and discrete (flexion and extension) reaching movements of various amplitudes to differently sized targets. The kinematic properties of the recorded movements were analyzed and compared in detail. The cyclical, ongoing movements differed markedly from the discrete movements as well as from the first and last half-cycles of a bout of cyclical movements, especially in terms of their symmetry ratio. These effects were largely independent of amplitude, target size and movement direction (flexion-extension). The results obtained ruled out perspective (a) and, in principle, left open perspectives (b) and (c). However, the observed kinematic features were not readily accounted for by the specific dynamical models that have been proposed under perspectives (b) and (c). Future modeling attempts should explicate the dynamics of initiation and abortion of both discrete and cyclical movements.
在运动控制的文献中，可以辨别出关于离散运动和周期性运动之间关系的三种理论观点：（a）周期性运动是串联的离散运动；（b）离散运动是周期性运动的一种极限情况，以及（c）离散运动和周期性运动是运动原基，它们可以组合但不能相互简化。为了检验这些观点的合理性，16名参与者对不同大小的目标进行了各种幅度的周期性和离散（屈伸）伸展运动。对记录的运动的运动学特性进行了详细分析和比较。周期性的持续运动与离散运动以及一轮周期性运动的第一个和最后半个周期明显不同，特别是在它们的对称比率方面。这些影响在很大程度上与幅度、目标大小和运动方向（屈伸）无关。获得的结果排除了观点（a），原则上，观点（b）和（c）仍未确定。然而，观察到的运动学特征不容易被在观点（b）和（c）下提出的特定动力学模型所解释。未来的建模尝试应该阐明离散运动和周期性运动的启动和终止动力学。
