Uncontrolled manifold hypothesis: Organization of leg joint variance in humans while walking in a wide range of speeds
Uncontrolled manifold hypothesis: Organization of leg joint variance in humans while walking in a wide range of speeds
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DOI：
10.1016/j.humov.2017.08.019
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发表时间：
2018-02-01
影响因子：
2.1
通讯作者：
Micera, Silvestro
中科院分区：
文献类型：
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作者：
Monaco, Vito;Tropea, Peppino;Micera, Silvestro
本研究旨在利用不受控制流形（UCM）理论研究行走过程中关节角度变化的组织。我们测试了两个假设：1 .在站立阶段关节角度变化的协调机制与稳定质心（CoM）位置的运动学协同作用是相容的；2。行走速度影响到与UCM正交的方差分量。8名健康受试者（26.0 +/- 2.0岁）在跑步机上以5种标准速度（从0.62 +/- 0.03 m/s到1.15 +/- 0.07 m/s）稳定行走。关节角度和足部方向以及CoM位置的组件分别被用作UCM实现的基本变量和任务性能。采用方差分析方法分析速度、时间事件和方差分量对关节角空间数据方差分布的影响。结果证实了假设，即基本变量的方差是结构化的，以便在所有速度下将CoM位置的跨步变异性最小化。值得注意的是，在推进阶段，两个方差分量都增加了，尽管与UCM平行的总是比正交的大。因此，观察到的运动协同作用应该有助于完成两个步骤之间的有效过渡。结果还表明，步行速度不影响元素变量相关方差在UCM上和与UCM正交的划分。因此，在不同的速度下，踝关节变化的组织结构几乎保持不变。
This study aimed at investigating the organization of joint angle variability during walking by using the uncontrolled manifold (UCM) theory. We tested two hypotheses: i. the coordinative mechanism underlying joint angle variance during the stance phase is compatible with a kinematic synergy that stabilizes the centre of mass (CoM) position; ii. the walking speed affects the variance components onto and orthogonal to the UCM.Eight healthy subjects (26.0 +/- 2.0 years old) steadily walked on a treadmill at five normalised speeds (from 0.62 +/- 0.03 m/s to 1.15 +/- 0.07 m/s). Joint angles and foot orientation, and components of the CoM position were, respectively, used as elemental variables and task performance for the UCM implementation. The effect of speed, time events, and variance components on the distribution of data variance in the space of joint angles was analyzed by the ANOVA test.Results corroborated the hypothesis that the variance of elemental variables is structured in order to minimize the stride-to-stride variability of the CoM position, at all speeds. Noticeably, both variance components increase during the propulsive phase, albeit that parallel to the UCM was always grater than the orthogonal one. Accordingly, the observed kinematic synergy is supposed to contribute to accomplishing an efficient transition between two steps. Results also revealed that the walking speed does not affect the partitioning of elemental variables-related variance onto and orthogonal to the UCM. Accordingly, the organization of leg joint variance underlying the stabilization of CoM position remains almost unaltered across speeds.