Effects of walking velocity on vertical head and body movements during locomotion
Effects of walking velocity on vertical head and body movements during locomotion
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DOI：
10.1007/s002210050781
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发表时间：
1999-07-01
影响因子：
2
通讯作者：
Cohen, B
中科院分区：
文献类型：
--
作者：
Hirasaki, E;Moore, ST;Cohen, B
4在不同的行走速度范围内研究躯干和头部的运动特征，以确定步长、步频、头部垂直平移、头部的俯仰旋转和俯仰躯干旋转之间的关系作为步态速度的函数。受试者(26~44岁)以0.6~2.2m/S的速度在直线跑步机上行走。将头部和躯干建模为刚体，并使用基于视频的运动分析系统确定旋转和平移。当步行速度达到1.2m/S时，头部俯仰在空间上几乎没有移动，头部相对于躯干的俯仰是对躯干俯仰的补偿。随着行走速度的增加，躯干螺距基本保持不变，但出现了显著的头部平移。这种头部平移导致了补偿性头部在空间中的俯仰，它倾向于将头部指向受试者前面的一个固定点，该固定点在行走速度方面保持大致不变。头部平移和旋转的优势频率在0.6m/S时为1.4~2.2m/S时的2.5 Hz。在0.8~1.8m/S范围内，受试者倾向于增加步长而不是步频来加快步速，并将头部运动的优势频率维持在接近2.0 Hz。当步行速度超过1.2m/S时，空间头距与垂直头部平移高度一致，并具有补偿作用。在1.2m/1.8m/S范围内，头部垂直平移的功率谱调谐最大，步行速度与头部和躯干运动的关系最线性。我们将其定义为关于头部-躯干协调的最佳行走速度范围。当步速低于1.2m/S和高于1.8m/S时，头部和躯干运动的协调性较差，提示在最佳步速范围内，采用两种机制来维持稳定的头部固定距离。每种机构对头部方向的相对贡献取决于头部运动的频率，从而取决于行走速度。考虑到代偿性头部俯仰的频率特性，我们推测，低速行走时，代偿性头部俯仰运动主要由角前庭结肠反射(AVCR)产生，而在较高速度时，代偿性头部俯仰运动主要由线性前庭结肠反射(LVCR)产生。
4Trunk and head movements were characterized over a wide range of walking speeds to determine the relationship between stride length, stepping frequency, vertical head translation, pitch rotation of the head, and pitch trunk rotation as a function of gait velocity. Subjects (26-44 years old) walked on a linear treadmill at velocities of 0.6-2.2 m/s. The head and trunk were modeled as rigid bodies, and rotation and translation were determined using a video-based motion analysis system. At walking speeds up to 1.2 m/s there was little head pitch movement in space, and the head pitch relative to the trunk was compensatory for trunk pitch. As walking velocity increased, trunk pitch remained approximately invariant, but a significant head translation developed. This head translation induced compensatory head pitch in space, which tended to point the head at a fixed point in front of the subject that remained approximately invariant with regard to walking speed. The predominant frequency of head translation and rotation was restricted to a narrow range from 1.4 Hz at 0.6 m/s to 2.5 Hz at 2.2 m/s. Within the range of 0.8-1.8 m/s, subjects tended to increase their stride length rather than step frequency to walk faster, maintaining the predominant frequency of head movement at close to 2.0 Hz. At walking speeds above 1.2 m/s, head pitch in space was highly coherent with, and compensatory for, vertical head translation. In the range 1.2-1.8 m/s, the power spectrum of vertical head translation was the most highly tuned, and the relationship between walking speed and head and trunk movements was the most linear. We define this as an optimal range of walking velocity with regard to head-trunk coordination. The coordination of head and trunk movement was less coherent at walking velocities below 1.2 m/s and above 1.8 m/s. These results suggest that two mechanisms are utilized to maintain a stable head fixation distance over the optimal range of walking velocities. The relative contribution of each mechanism to head orientation depends on the frequency of head movement and consequently on walking velocity. From consideration of the frequency characteristics of the compensatory head pitch, we infer that compensatory head pitch movements may be produced predominantly by the angular vestibulocollic reflex (aVCR) at low walking speeds and by the linear vestibulocollic reflex (lVCR) at the higher speeds.