Balance responses to lateral perturbations in human treadmill walking
Balance responses to lateral perturbations in human treadmill walking
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DOI：
10.1242/jeb.042572
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发表时间：
2010-08-01
影响因子：
2.8
通讯作者：
Gjaltema, W. A.
中科院分区：
文献类型：
--
作者：
Hof, A. L.;Vermerris, S. M.;Gjaltema, W. A.
在跑步机上行走期间，10名人类受试者（平均年龄20岁）受到向左或向右的100 ms推或拉的各种幅度和步态周期的各个阶段的扰动。平衡是通过（1）一个步进策略（协同作用），其中脚在下一个步骤是定位在一个固定的距离外的“外推质心”，和（2）外侧脚踝策略，其中包括一个内侧或外侧运动的压力中心在脚底。外推质心定义为质心位置加上质心速度乘以与受试者腿长相关的参数。踝关节策略是最快的，机械延迟约为200 ms（步幅的20%），但它可以移动压力中心不超过2 cm。步进策略在脚放置之前需要至少300 ms（步幅的30%），但范围为20 cm。当反应时间足够时，总响应的大小与我们的假设非常一致：平均压力中心（脚）位置是外推质心的恒定距离。如果反应时间福尔斯缩短，则在下一步骤中应用进一步的校正。在这里研究的健康受试者中，不需要进一步的校正，所以在两步（一步）内恢复平衡。
During walking on a treadmill 10 human subjects (mean age 20 years) were perturbed by 100 ms pushes or pulls to the left or the right, of various magnitudes and in various phases of the gait cycle. Balance was maintained by (1) a stepping strategy (synergy), in which the foot at the next step is positioned a fixed distance outward of the 'extrapolated centre of mass', and (2) a lateral ankle strategy, which comprises a medial or lateral movement of the centre of pressure under the foot sole. The extrapolated centre of mass is defined as the centre of mass position plus the centre of mass velocity multiplied by a parameter related to the subject's leg length. The ankle strategy is the fastest, with a mechanical delay of about 200 ms (20% of a stride), but it can displace the centre of pressure no more than 2 cm. The stepping strategy needs at least 300 ms (30% of a stride) before foot placement, but has a range of 20 cm. When reaction time is sufficient, the magnitude of the total response is in good agreement with our hypothesis: mean centre of pressure (foot) position is a constant distance outward of the extrapolated centre of mass. If the reaction time falls short, a further correction is applied in the next step. In the healthy subjects studied here, no further corrections were necessary, so balance was recovered within two steps (one stride).