Postural adjustments accompanying fast pointing movements in standing, sitting and lying adults
Postural adjustments accompanying fast pointing movements in standing, sitting and lying adults
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DOI：
10.1007/s002210050394
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发表时间：
1998-05-01
影响因子：
2
通讯作者：
Hadders-Algra, M
中科院分区：
文献类型：
--
作者：
van der Fits, IBM;Klip, AWJ;Hadders-Algra, M
目前的研究评估了不同的位置，不同的身体支持的量，对姿势控制的影响，在快速的指向运动。研究人员对14名成年受试者进行了站立、各种坐姿和躺姿的研究。在一系列标准的单侧手臂运动过程中，记录手臂、颈部、躯干和上肢肌肉的多面肌电图（emg）和运动学。另外两个系列，包括双侧手臂运动和单侧手臂运动与额外的重量，进行评估额外的任务负荷是否影响坐姿和站立姿势的调整不同。使用了两种指向策略——尽管指令相同。7名受试者在运动过程中肘部伸展。他们使用三角肌（DE）作为原动机（DE组）。其他7名受试者以肱二头肌（BB组）为原动力，肘关节轻微弯曲。这两种策略对姿势调整有不同的影响：与DE组相比，bb组的姿势活动更少，而且时间更长。预期的体位肌肉活动仅在站立时出现在DE组。在所有体位和任务负荷条件下，背侧体位肌肉在腹侧拮抗剂之前被激活。激活率、时间和（在较小程度上）背肌活动的幅度与位置有关。位置依赖性主要见于腰伸肌（LE）和腘绳肌（HAM）。LE和HAM的肌电波幅也受身体几何形状（躯干和骨盆位置）的影响。体位和体位对颈部和胸伸肌活动的影响很小。上下体位肌肉的这种行为差异表明，它们可以执行不同的体位任务：下部肌肉更多地参与保持物体中心在支撑面范围内，而上部肌肉则参与抵消运动开始时产生的反作用力。通过进行双侧运动和（在较小程度上）在加载的单边运动中增加任务负荷，以类似的方式影响站立和坐着时姿势调整的时间和数量特征。这种效应主要出现在反应的早期（原动机开始后100毫秒内）。这表明前馈或预期机制在特定任务的姿势调节中起主要作用。
The present study evaluated the effect of different positions, which varied in the amount of bodily support, on postural control during fast pointing movements. Fourteen adult subjects were studied in standing, various sitting and lying positions. Multiple surface electromyograms (EMGs) of arm, neck, trunk and upper leg muscles and kinematics were recorded during a standard series of unilateral arm movements. Two additional series, consisting of bilateral arm movements and unilateral arm movements with an additional weight, were performed to assess whether additional task-load affected postural adjustments differently in a sitting and standing position. Two pointing strategies were used - despite identical instructions. Seven subjects showed an elbow extension throughout the movements. They used the deltoid (DE) as the prime mover (DE group). The other seven subjects performed the movement with a slight elbow flexion and used the biceps brachii (BB) as the prime mover (BB group). The two strategies had a differential effect on the postural adjustments: postural activity was less and substantially later in the BB-group than in the DE group. Anticipatory postural muscle activity was only present in the DE group during stance. In all positions and task-load conditions the dorsal postural muscles were activated before their ventral antagonists. The activation rate, the timing and - to a lesser extent - the amplitude of the dorsal muscle activity was position dependent. The position dependency was mainly found in the caudally located lumbar extensor (LE) and hamstrings (HAM) muscles. The EMG amplitude of LE and HAM was also affected by body geometry (trunk and pelvis position). Position and body geometry had only a minor effect on the activity of the neck and thoracic extensor muscles. This difference in behaviour of lower and upper postural muscles suggests that they could serve different postural tasks: the lower muscles being more involved in keeping the centre of mass within the limits of the support surface, and the upper ones in counteracting the reaction forces generated by movement onset. Increasing task-load by performing bilateral movements and - to a minor extent - during loaded unilateral movements affected the temporal and quantitative characteristics of the postural adjustments during standing and sitting in a similar way. The effect was present mainly during the early part of the response (within 100 ms after prime mover onset). This suggests that feedforward or anticipatory mechanisms play a major role in the task-specific modulation of postural adjustments.