Dounskaia N V, Swinnen S P, Walter C B, Spaepen A J, Verschueren S M
The Institute of Control Sciences of the Russian Academy of Science, Moscow.
Exp Brain Res. 1998 Aug;121(3):239-54. doi: 10.1007/s002210050457.
The present paper focused on the role of mechanical factors arising from the multijoint structure of the musculoskeletal system and their use in the control of different patterns of cyclical elbow-wrist movements. Across five levels of cycling frequency (from 0.45 Hz up to 3.05 Hz), three movement patterns were analyzed: (1) unidirectional, including rotations at the elbow and wrist in the same direction; (2) bidirectional, with rotation at the joints in opposite directions, and (3) free-wrist pattern, which is characterized by alternating flexions and extensions at the elbow with the wrist relaxed. Angular position of both joints and electromyographic activity of biceps, triceps, the wrist flexor, and the wrist extensor were recorded. It was demonstrated that control at the elbow was principally different from control at the wrist. Elbow control in all three patterns was similar to that typically observed during single-joint movements: elbow accelerations-decelerations resulted from alternating activity of the elbow flexor and extensor and were largely independent of wrist motion at all frequency plateaus. The elbow muscles were responsible not only for the elbow movement, but also for the generation of interactive torques that played an important role in wrist control. There were two types of interactive torques exerted at the wrist: inertial torque arising from elbow motion and restraining torque arising from physical limits imposed on wrist rotation. These interactive torques were the primary source of wrist motion, whereas the main function of wrist-muscle activity was to intervene with the interactive effects and to adjust the wrist movement to comply with the required coordination pattern. The unidirectional pattern was more in agreement with interactive effects than the bidirectional pattern, thus causing their differential difficulty at moderate cycle frequencies. When cycling frequency was further increased, both the unidirectional and bidirectional movements lost their individual features and acquired features of the free-wrist pattern. The deterioration of the controlled patterns at high cycling frequencies suggests a crucial role for proprioceptive information in wrist control. These results are supportive of a hierarchical organization of control with respect to elbow-wrist coordination, during which the functions of control at the elbow and wrist are principally different: the elbow muscles generate movement of the whole linkage and the wrist muscles produce corrections of the movement necessary to fulfill the task.
本文聚焦于肌肉骨骼系统多关节结构产生的机械因素的作用，以及这些因素在控制不同模式的周期性肘腕运动中的应用。在五个骑行频率水平（从0.45赫兹到3.05赫兹）上，分析了三种运动模式：（1）单向模式，包括肘部和腕部沿同一方向旋转；（2）双向模式，关节沿相反方向旋转；（3）自由腕模式，其特征是肘部交替屈伸，腕部放松。记录了两个关节的角位置以及肱二头肌、肱三头肌、腕屈肌和腕伸肌的肌电活动。结果表明，肘部控制与腕部控制存在显著差异。在所有三种模式下，肘部控制与单关节运动中通常观察到的情况相似：肘部的加速 - 减速是由肘部屈肌和伸肌的交替活动引起的，并且在所有频率平台上很大程度上独立于腕部运动。肘部肌肉不仅负责肘部运动，还负责产生在腕部控制中起重要作用的相互作用扭矩。在腕部施加了两种类型的相互作用扭矩：由肘部运动产生的惯性扭矩和对腕部旋转施加的物理限制产生的约束扭矩。这些相互作用扭矩是腕部运动的主要来源，而腕部肌肉活动的主要功能是干预相互作用效应，并调整腕部运动以符合所需的协调模式。单向模式比双向模式更符合相互作用效应，因此在中等循环频率下导致它们的难度差异。当骑行频率进一步增加时，单向和双向运动都失去了各自的特征，并获得了自由腕模式的特征。在高骑行频率下受控模式的恶化表明本体感觉信息在腕部控制中起着关键作用。这些结果支持了关于肘腕协调控制的层次组织，在此过程中，肘部和腕部的控制功能存在显著差异：肘部肌肉产生整个联动装置的运动，腕部肌肉对完成任务所需的运动进行校正。
