Aruin A S, Forrest W R, Latash M L
Department of Kinesiology, Pennsylvania State University, University Park 16802, USA.
Electroencephalogr Clin Neurophysiol. 1998 Aug;109(4):350-9. doi: 10.1016/s0924-980x(98)00029-0.
The purpose of this study was to investigate anticipatory postural adjustments (APAs) in standing subjects who performed a standard motor action triggering a standard postural perturbation (releasing a 2.2 kg load from extended arms) in conditions of different stability requirements.
The degree of stability was varied either by balancing on special boards with long and narrow support beams or by instructions to the subjects. In the first series of experiments 13 subjects stood on the board facing either perpendicular to the beam (instability in a sagittal plane) or along the beam (instability in frontal plane); different widths of the beam were used to vary the degree of instability. During the second series of experiments (6 subjects) inclined and one-legged postures were used to induce instability in sagittal and frontal planes respectively. EMG activity of rectus abdominis, erector spinae, rectus femoris, biceps femoris, tibialis anterior, and soleus muscles were recorded. Statistical methods included repeated measures analysis of variance (ANOVA) with direction of instability and level of instability being major factors, descriptive statistics, and post hoc Student's t tests.
The integral measure of changes in the background electromyographic activity of postural muscles during APAs depended on two factors related to the postural task: (1) standing on a platform with a narrow support area led to an attenuation of the APAs; and (2) these effects were stronger when instability was in a sagittal rather than in the frontal plane. The anticipatory component in the displacement of the center of pressure did not show a clear attenuation that would depend on the direction of instability.
We suggest a hypothesis that, in conditions of high stability demands, the central nervous system may suppress APAs as a protection against their possible destabilizing effects. These effects are more pronounced when the direction of an expected perturbation is in the plane of instability.
本研究旨在调查在不同稳定性要求条件下，执行引发标准姿势扰动的标准运动动作（从伸展的手臂释放2.2千克重物）的站立受试者的预期姿势调整（APA）。
通过在带有长而窄支撑梁的特殊板子上保持平衡或向受试者发出指令来改变稳定性程度。在第一组实验中，13名受试者站在板子上，要么垂直于梁（矢状面不稳定），要么沿着梁（额状面不稳定）；使用不同宽度的梁来改变不稳定程度。在第二组实验（6名受试者）中，分别采用倾斜和单腿姿势在矢状面和额状面诱发不稳定。记录腹直肌、竖脊肌、股直肌、股二头肌、胫前肌和比目鱼肌的肌电图活动。统计方法包括以不稳定方向和不稳定程度为主要因素的重复测量方差分析（ANOVA）、描述性统计以及事后学生t检验。
APA期间姿势肌肉背景肌电图活动变化的整体测量取决于与姿势任务相关的两个因素：（1）站在支撑面积狭窄的平台上会导致APA减弱；（2）当不稳定在矢状面而非额状面时，这些影响更强。压力中心位移中的预期成分并未表现出明显的取决于不稳定方向的减弱。
我们提出一个假设，即在高稳定性要求的条件下，中枢神经系统可能会抑制APA，以防止其可能的破坏稳定作用。当预期扰动的方向在不稳定平面内时，这些影响更为明显。
