Thresholds for step initiation induced by support-surface translation: a dynamic center-of-mass model provides much better prediction than a static model
Thresholds for step initiation induced by support-surface translation: a dynamic center-of-mass model provides much better prediction than a static model
复制标题
DOI：
10.1016/s0021-9290(99)00199-2
复制
发表时间：
2000-03-01
影响因子：
2.4
通讯作者：
Perry, SD
中科院分区：
文献类型：
--
作者：
Pai, YC;Maki, BE;Perry, SD
从理论上讲，为了恢复平衡而启动一个步骤的需要，可以通过仅基于质心(COM)相对于支撑底座(BOS)的位移的静态模型来预测，或者通过基于COM位移和速度之间的相互作用的动态模型来预测。这项研究的目的是确定动态模型是否比静态模型提供了关于响应移动平台扰动的步进需求的更好的预测。对10名健康的年轻人进行了COM相平面轨迹的测定，其中支撑平台在前后方向上以三种不同的加速度水平平移。将这些轨迹与静态和动态COM模型预测的步长启动阈值进行比较。采用单连杆+脚的生物力学模型，以测量的平台加速度为输入，对COM运动的终止进行了数学模拟。使用优化例程来确定COM状态空间中的稳定边界，以便建立动态阈值，在该阈值处必须启动补偿步骤以恢复平衡。在静态模型中，如果COM位移超过BOS限制，则达到启动步骤的阈值。动态模型在预测恢复平衡所需的步进反应方面表现出比静态模型高得多的准确性：动态模型正确预测了所有步进反应的71%，而静态模型只有11%。这些结果支持这样的命题，即中枢神经系统必须对动态效应(即COM速度)以及COM位移做出反应并加以控制，以保持相对于现有BOS的稳定性而无需步进，(C)2000爱思唯尔科学有限公司。保留所有权利。
The need to initiate a step in order to recover balance could, in theory, be predicted by a static model based solely on displacement of the center of mass (COM) with respect to the base of support (BOS), or by a dynamic model based on the interaction between COM displacement and velocity. The purpose of this study was to determine whether the dynamic model provides better prediction than the static model regarding the need to step in response to moving-platform perturbation. The COM phase plane trajectories were determined for 10 healthy young adults for trials where the supporting platform was translated at three different acceleration levels in anterior and posterior directions. These trajectories were compared with the thresholds for step initiation predicted by the static and dynamic COM models. A single-link-plus-foot biomechanical model was employed to mathematically simulate termination of the COM movement, without stepping, using the measured platform acceleration as the input. An optimization routine was used to determine the stability boundaries in COM state space so as to establish the dynamic thresholds where a compensatory step must be initiated in order to recover balance. In the static model, the threshold for step initiation was reached if the COM was displaced beyond the BOS limits. The dynamic model showed substantially better accuracy than the static model in predicting the need to step in order to recover balance: 71% of all stepping responses predicted correctly by the dynamic model versus only 11% by the static model. These results support the proposition that the central nervous system must react to and control dynamic effects, i.e. COM velocity, as well as COM displacement in order to maintain stability with respect to the existing BOS without stepping, (C) 2000 Elsevier Science Ltd. All rights reserved.