Siegmund Gunter P, Sanderson David J, Inglis J Timothy
School of Human Kinetics, University of British Columbia, Vancouver, Canada.
Exp Brain Res. 2002 Jun;144(3):314-21. doi: 10.1007/s00221-002-1048-2. Epub 2002 Mar 7.
The muscle and kinematic responses of subjects exposed to postural perturbations have been shown to vary with platform acceleration when this acceleration was covaried with platform velocity or displacement. The purpose of the current study was to isolate platform acceleration and examine its effect on the neck muscle response and head kinematics of seated subjects exposed to anterior perturbations. Thirty-six subjects (20 females, 16 males) underwent two blocks of 36 perturbations. Three different perturbations with peak accelerations of 7.7, 14.7, and 21.7 m/s(2) up to a common velocity of 0.5 m/s were used. In one block, subjects received an audible warning corresponding to the platform acceleration magnitude, and in the other block, no advance warning was given. Onset and amplitude of the sternocleidomastoid and cervical paraspinal muscle responses were measured using surface electromyography. Kinematic measures included linear and angular accelerations and displacements of the head. The results showed no differences in either the preperturbation posture or the muscle or kinematic responses between the warned and unwarned trials. Significant differences were observed in the onset and amplitude of the muscle and kinematic variables with perturbation acceleration, although these response differences were not linearly graded with perturbation acceleration. Gradation of muscle activation times has not been previously observed in postural perturbation studies, and their gradation with platform acceleration in the current study suggested that platform acceleration was a strong regulator of the reflex muscle response in postural perturbations.
当平台加速度与平台速度或位移协变时，已表明暴露于姿势扰动的受试者的肌肉和运动反应会随平台加速度而变化。本研究的目的是分离平台加速度，并检查其对暴露于向前扰动的坐位受试者颈部肌肉反应和头部运动学的影响。三十六名受试者（20名女性，16名男性）接受了两个包含36次扰动的组块。使用了三种不同的扰动，峰值加速度分别为7.7、14.7和21.7 m/s²，直至共同速度0.5 m/s。在一个组块中，受试者收到与平台加速度大小相对应的听觉警告，而在另一个组块中，未给出预先警告。使用表面肌电图测量胸锁乳突肌和颈旁肌反应的起始和幅度。运动学测量包括头部的线性和角加速度及位移。结果表明，在有警告和无警告试验之间，扰动前姿势、肌肉或运动反应均无差异。观察到肌肉和运动学变量的起始和幅度随扰动加速度存在显著差异，尽管这些反应差异并非与扰动加速度呈线性分级。在姿势扰动研究中，此前尚未观察到肌肉激活时间的分级，而在本研究中它们随平台加速度的分级表明，平台加速度是姿势扰动中反射性肌肉反应的强调节因子。
