Virji-Babul N, Cooke J D, Brown S H
Faculty of Applied Health Sciences, Elborn College, University of Western Ontario, London, Canada.
Exp Brain Res. 1994;99(2):338-46. doi: 10.1007/BF00239600.
We have examined the kinematics and muscle activation patterns of single joint elbow movements made in the vertical plane. Movements of different amplitudes were performed during a visual, step-tracking task. By adjusting shoulder position, both elbow flexion and extension movements were made under three conditions: (a) in the horizontal plane, (b) in the vertical plane against gravity, and (c) in the vertical plane with gravity. Regardless of the gravitational load, all movements were characterized by time symmetric velocity profiles. In addition, no differences were found in the relationships between movement duration, peak velocity, and movement amplitude in movements with or against gravity. The pattern of muscle activation was influenced however, by the gravitational load. Both flexion and extension movements made with gravity were characterized by a reciprocally organized pattern of muscle activity in which phasic agonist activity was followed by phasic antagonist activity. Flexion and extension movements made against gravity were characterized by early phasic antagonist activity occurring at about the same time as the initial agonist burst. These findings suggest that EMG patterns are modified in order to preserve a common temporal structure in the face of different gravitational loads.
我们研究了在垂直平面内进行的单关节肘部运动的运动学和肌肉激活模式。在视觉步跟踪任务中进行了不同幅度的运动。通过调整肩部位置，在三种条件下进行了肘部屈伸运动：(a) 在水平面内，(b) 在垂直平面内对抗重力，以及(c) 在垂直平面内借助重力。无论重力负荷如何，所有运动均具有时间对称的速度曲线特征。此外，在有重力或对抗重力的运动中，运动持续时间、峰值速度和运动幅度之间的关系未发现差异。然而，肌肉激活模式受重力负荷影响。借助重力进行的屈伸运动均具有相互组织的肌肉活动模式，其中相位性激动剂活动之后是相位性拮抗剂活动。对抗重力进行的屈伸运动的特征是，早期相位性拮抗剂活动与初始激动剂爆发大致同时出现。这些发现表明，肌电图模式会发生改变，以便在面对不同重力负荷时保持共同的时间结构。
