Aruin A S, Latash M L
Department of Physical Medicine and Rehabilitation, Rush-Presbyterian St. Luke's Medical Center, Chicago, IL 60612, USA.
Exp Brain Res. 1995;103(2):323-32. doi: 10.1007/BF00231718.
Healthy subjects performed bilateral fast shoulder movements in different directions while standing on a force platform. Anticipatory postural adjustments were seen as changes in the electrical activity of postural muscles as well as displacements of the center of pressure and center of gravity. Postural muscle pairs of agonist-antagonist commonly demonstrated triphasic patterns starting prior to the first electromyographic (EMG) burst in the prime-mover muscle. Proximal postural muscles demonstrated the largest anticipatory increase in the background activity during movements in one of the two opposite directions (forward or backwards). These changes progressively decreased when movements deviated from the preferred direction and frequently disappeared during movements in the opposite direction. The patterns in distal muscles varied across subjects and could demonstrate larger anticipatory changes during movements forward and backwards as compared to movements in intermediate directions. Bilateral addition of inertial loads to the wrists did not change the general anticipatory patterns, while making some of their features more pronounced. Anticipatory postural adjustments were followed by later changes in the activity of postural muscles, also reflected in the mechanical variables. Changes in leg joint angles revealed a "hip-ankle strategy" during shoulder flexions and an "ankle strategy" during shoulder extensions. The study demonstrates different behaviors of proximal and distal muscles during anticipatory postural adjustments in preparation for fast arm movements. We suggest that the proximal muscles produce a general pattern of postural adjustments, while distal muscles take care of fine adjustments that are more likely to vary across subjects.
健康受试者站在测力平台上进行不同方向的双侧快速肩部运动。预期姿势调整表现为姿势肌肉电活动的变化以及压力中心和重心的位移。原动肌中第一肌电图（EMG）爆发之前，主动肌-拮抗肌的姿势肌肉对通常呈现三相模式。近端姿势肌肉在两个相反方向之一（向前或向后）的运动过程中，背景活动出现最大的预期增加。当运动偏离首选方向时，这些变化逐渐减少，并且在相反方向的运动过程中经常消失。远端肌肉的模式因受试者而异，与中间方向的运动相比，向前和向后运动期间可能表现出更大的预期变化。在手腕双侧增加惯性负荷并没有改变一般的预期模式，只是使其一些特征更加明显。预期姿势调整之后是姿势肌肉活动的后期变化，这也反映在力学变量中。腿部关节角度的变化显示，肩部屈曲时采用“髋-踝策略”，肩部伸展时采用“踝策略”。该研究表明，在为快速手臂运动做准备的预期姿势调整过程中，近端和远端肌肉的行为不同。我们认为，近端肌肉产生姿势调整的一般模式，而远端肌肉负责更可能因受试者而异的精细调整。
